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	$180.94	8.624%	$196.5443	$196.54	$196.55	$196.50
Purchase #2	$241.26	3.623%	$250.0008	$250.00	$250.00	$250.00
Purchase #3	$53.46	12.509%	$60.1473	$60.15	$60.15	$60.10
Purchase #4	$43.90	6.459%	$46.7355	$46.74	$46.75	$46.70
Purchase #5	$148.28	10.873%	$164.4025	$164.40	$164.40	$164.40
Purchase #6	$169.26	13.796%	$192.6111	$192.61	$192.60	$192.60
Purchase #7	$240.33	12.163%	$269.5613	$269.56	$269.55	$269.60
7 purchase totals =	$1,077.43		$1,180.0028	$1,180.00	$1,180.00	$1,179.90