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	$238.59	6.115%	$253.1798	$253.18	$253.20	$253.20
Purchase #2	$48.83	6.309%	$51.9107	$51.91	$51.90	$51.90
Purchase #3	$51.40	6.749%	$54.869	$54.87	$54.85	$54.90
Purchase #4	$229.78	12.617%	$258.7713	$258.77	$258.75	$258.80
Purchase #5	$161.41	6.334%	$171.6337	$171.63	$171.65	$171.60
Purchase #6	$188.61	12.523%	$212.2296	$212.23	$212.25	$212.20
Purchase #7	$232.83	8.683%	$253.0466	$253.05	$253.05	$253.00
7 purchase totals =	$1,151.45		$1,255.6407	$1,255.64	$1,255.65	$1,255.60