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	$126.79	5.429%	$133.6734	$133.67	$133.65	$133.70
Purchase #2	$240.82	6.626%	$256.7767	$256.78	$256.80	$256.80
Purchase #3	$211.63	10.165%	$233.1422	$233.14	$233.15	$233.10
Purchase #4	$115.42	10.414%	$127.4398	$127.44	$127.45	$127.40
Purchase #5	$104.67	6.237%	$111.1983	$111.20	$111.20	$111.20
Purchase #6	$145.90	3.753%	$151.3756	$151.38	$151.40	$151.40
Purchase #7	$240.84	13.734%	$273.917	$273.92	$273.90	$273.90
7 purchase totals =	$1,186.07		$1,287.5230	$1,287.53	$1,287.55	$1,287.50