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	$193.45	4.149%	$201.4762	$201.48	$201.50	$201.50
Purchase #2	$123.64	6.728%	$131.9585	$131.96	$131.95	$132.00
Purchase #3	$162.73	8.478%	$176.5262	$176.53	$176.55	$176.50
Purchase #4	$100.74	4.326%	$105.098	$105.10	$105.10	$105.10
Purchase #5	$83.47	6.738%	$89.0942	$89.09	$89.10	$89.10
Purchase #6	$192.82	12.285%	$216.5079	$216.51	$216.50	$216.50
Purchase #7	$47.59	12.679%	$53.6239	$53.62	$53.60	$53.60
7 purchase totals =	$904.44		$974.2849	$974.29	$974.30	$974.30