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	$125.89	5.761%	$133.1425	$133.14	$133.15	$133.10
Purchase #2	$100.78	10.360%	$111.2208	$111.22	$111.20	$111.20
Purchase #3	$88.86	4.385%	$92.7565	$92.76	$92.75	$92.80
Purchase #4	$198.78	12.362%	$223.3532	$223.35	$223.35	$223.40
Purchase #5	$116.83	8.755%	$127.0585	$127.06	$127.05	$127.10
Purchase #6	$113.78	5.130%	$119.6169	$119.62	$119.60	$119.60
Purchase #7	$42.69	4.188%	$44.4779	$44.48	$44.50	$44.50
7 purchase totals =	$787.61		$851.6263	$851.63	$851.60	$851.70