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	$211.51	5.639%	$223.437	$223.44	$223.45	$223.40
Purchase #2	$180.89	6.352%	$192.3801	$192.38	$192.40	$192.40
Purchase #3	$151.25	3.593%	$156.6844	$156.68	$156.70	$156.70
Purchase #4	$76.95	7.497%	$82.7189	$82.72	$82.70	$82.70
Purchase #5	$143.75	3.110%	$148.2206	$148.22	$148.20	$148.20
Purchase #6	$145.55	6.532%	$155.0573	$155.06	$155.05	$155.10
Purchase #7	$150.37	10.292%	$165.8461	$165.85	$165.85	$165.80
7 purchase totals =	$1,060.27		$1,124.3444	$1,124.35	$1,124.35	$1,124.30