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	$54.94	12.305%	$61.7004	$61.70	$61.70	$61.70
Purchase #2	$243.25	4.123%	$253.2792	$253.28	$253.30	$253.30
Purchase #3	$19.61	10.159%	$21.6022	$21.60	$21.60	$21.60
Purchase #4	$78.53	13.435%	$89.0805	$89.08	$89.10	$89.10
Purchase #5	$234.27	9.665%	$256.9122	$256.91	$256.90	$256.90
Purchase #6	$150.94	7.413%	$162.1292	$162.13	$162.15	$162.10
Purchase #7	$195.48	13.375%	$221.6255	$221.63	$221.65	$221.60
7 purchase totals =	$977.02		$1,066.3292	$1,066.33	$1,066.40	$1,066.30