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	$191.94	11.228%	$213.491	$213.49	$213.50	$213.50
Purchase #2	$231.54	6.834%	$247.3634	$247.36	$247.35	$247.40
Purchase #3	$143.32	12.408%	$161.1031	$161.10	$161.10	$161.10
Purchase #4	$202.75	12.684%	$228.4668	$228.47	$228.45	$228.50
Purchase #5	$28.33	13.155%	$32.0568	$32.06	$32.05	$32.10
Purchase #6	$79.55	12.407%	$89.4198	$89.42	$89.40	$89.40
Purchase #7	$139.96	6.355%	$148.8545	$148.85	$148.85	$148.90
7 purchase totals =	$1,017.39		$1,120.7554	$1,120.75	$1,120.70	$1,120.90