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	$146.52	12.719%	$165.1559	$165.16	$165.15	$165.20
Purchase #2	$212.28	7.817%	$228.8739	$228.87	$228.85	$228.90
Purchase #3	$5.30	6.866%	$5.6639	$5.66	$5.65	$5.70
Purchase #4	$142.45	4.183%	$148.4087	$148.41	$148.40	$148.40
Purchase #5	$227.58	5.869%	$240.9367	$240.94	$240.95	$240.90
Purchase #6	$196.30	10.298%	$216.515	$216.52	$216.50	$216.50
Purchase #7	$77.78	5.211%	$81.8331	$81.83	$81.85	$81.80
7 purchase totals =	$1,008.21		$1,087.3872	$1,087.39	$1,087.35	$1,087.40