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	$79.88	10.847%	$88.5446	$88.54	$88.55	$88.50
Purchase #2	$236.29	10.145%	$260.2616	$260.26	$260.25	$260.30
Purchase #3	$52.28	13.646%	$59.4141	$59.41	$59.40	$59.40
Purchase #4	$176.80	8.112%	$191.142	$191.14	$191.15	$191.10
Purchase #5	$209.97	6.272%	$223.1393	$223.14	$223.15	$223.10
Purchase #6	$156.66	10.736%	$173.479	$173.48	$173.50	$173.50
Purchase #7	$138.81	11.814%	$155.209	$155.21	$155.20	$155.20
7 purchase totals =	$1,050.69		$1,151.1896	$1,151.18	$1,151.20	$1,151.10