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	$223.76	3.847%	$232.368	$232.37	$232.35	$232.40
Purchase #2	$28.25	11.242%	$31.4259	$31.43	$31.45	$31.40
Purchase #3	$42.90	3.595%	$44.4423	$44.44	$44.45	$44.40
Purchase #4	$212.27	10.115%	$233.7411	$233.74	$233.75	$233.70
Purchase #5	$250.81	7.306%	$269.1342	$269.13	$269.15	$269.10
Purchase #6	$143.29	7.138%	$153.518	$153.52	$153.50	$153.50
Purchase #7	$129.77	4.832%	$136.0405	$136.04	$136.05	$136.00
7 purchase totals =	$1,031.05		$1,100.6700	$1,100.67	$1,100.70	$1,100.50