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	$212.77	8.745%	$231.3767	$231.38	$231.40	$231.40
Purchase #2	$151.38	6.291%	$160.9033	$160.90	$160.90	$160.90
Purchase #3	$53.88	3.465%	$55.7469	$55.75	$55.75	$55.70
Purchase #4	$107.70	3.672%	$111.6547	$111.65	$111.65	$111.70
Purchase #5	$55.57	12.348%	$62.4318	$62.43	$62.45	$62.40
Purchase #6	$143.77	12.613%	$161.9037	$161.90	$161.90	$161.90
Purchase #7	$132.44	11.278%	$147.3766	$147.38	$147.40	$147.40
7 purchase totals =	$857.51		$931.3937	$931.39	$931.45	$931.40