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	$57.67	13.850%	$65.6573	$65.66	$65.65	$65.70
Purchase #2	$114.90	12.111%	$128.8155	$128.82	$128.80	$128.80
Purchase #3	$243.40	4.848%	$255.2	$255.20	$255.20	$255.20
Purchase #4	$206.48	8.341%	$223.7025	$223.70	$223.70	$223.70
Purchase #5	$180.65	13.842%	$205.6556	$205.66	$205.65	$205.70
Purchase #6	$118.27	11.527%	$131.903	$131.90	$131.90	$131.90
Purchase #7	$188.81	6.156%	$200.4331	$200.43	$200.45	$200.40
7 purchase totals =	$1,110.18		$1,211.3670	$1,211.37	$1,211.35	$1,211.40