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	$95.68	7.769%	$103.1134	$103.11	$103.10	$103.10
Purchase #2	$214.42	3.434%	$221.7832	$221.78	$221.80	$221.80
Purchase #3	$36.84	6.795%	$39.3433	$39.34	$39.35	$39.30
Purchase #4	$97.55	6.549%	$103.9385	$103.94	$103.95	$103.90
Purchase #5	$167.91	12.850%	$189.4864	$189.49	$189.50	$189.50
Purchase #6	$83.27	7.645%	$89.636	$89.64	$89.65	$89.60
Purchase #7	$71.61	6.684%	$76.3964	$76.40	$76.40	$76.40
7 purchase totals =	$767.28		$823.6972	$823.70	$823.75	$823.60