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	$244.53	10.287%	$269.6848	$269.68	$269.70	$269.70
Purchase #2	$211.53	5.402%	$222.9569	$222.96	$222.95	$223.00
Purchase #3	$129.51	3.158%	$133.5999	$133.60	$133.60	$133.60
Purchase #4	$93.73	5.148%	$98.5552	$98.56	$98.55	$98.60
Purchase #5	$231.61	10.632%	$256.2348	$256.23	$256.25	$256.20
Purchase #6	$18.55	9.184%	$20.2536	$20.25	$20.25	$20.30
Purchase #7	$40.71	7.732%	$43.8577	$43.86	$43.85	$43.90
7 purchase totals =	$970.17		$1,045.1429	$1,045.14	$1,045.15	$1,045.30