Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$183.53	13.340%	$208.0129	$208.01	$208.00	$208.00
Purchase #2	$107.53	7.659%	$115.7657	$115.77	$115.75	$115.80
Purchase #3	$113.59	13.251%	$128.6418	$128.64	$128.65	$128.60
Purchase #4	$168.53	4.459%	$176.0448	$176.04	$176.05	$176.00
Purchase #5	$97.63	12.548%	$109.8806	$109.88	$109.90	$109.90
Purchase #6	$198.75	12.500%	$223.5938	$223.59	$223.60	$223.60
Purchase #7	$159.33	12.119%	$178.6392	$178.64	$178.65	$178.60
7 purchase totals =	$1,028.89		$1,140.5788	$1,140.57	$1,140.60	$1,140.50