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	$29.43	9.610%	$32.2582	$32.26	$32.25	$32.30
Purchase #2	$33.79	10.321%	$37.2775	$37.28	$37.30	$37.30
Purchase #3	$211.62	5.404%	$223.0559	$223.06	$223.05	$223.10
Purchase #4	$79.25	12.741%	$89.3472	$89.35	$89.35	$89.30
Purchase #5	$207.35	7.792%	$223.5067	$223.51	$223.50	$223.50
Purchase #6	$208.34	10.696%	$230.624	$230.62	$230.60	$230.60
Purchase #7	$246.97	12.458%	$277.7375	$277.74	$277.75	$277.70
7 purchase totals =	$1,016.75		$1,113.8070	$1,113.82	$1,113.80	$1,113.80