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	$97.82	13.691%	$111.2125	$111.21	$111.20	$111.20
Purchase #2	$67.26	6.355%	$71.5344	$71.53	$71.55	$71.50
Purchase #3	$190.66	8.480%	$206.828	$206.83	$206.85	$206.80
Purchase #4	$195.63	7.524%	$210.3492	$210.35	$210.35	$210.30
Purchase #5	$113.85	5.188%	$119.7565	$119.76	$119.75	$119.80
Purchase #6	$190.37	13.729%	$216.5059	$216.51	$216.50	$216.50
Purchase #7	$221.81	13.222%	$251.1377	$251.14	$251.15	$251.10
7 purchase totals =	$1,077.40		$1,187.3242	$1,187.33	$1,187.35	$1,187.20