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	$213.83	8.109%	$231.1695	$231.17	$231.15	$231.20
Purchase #2	$49.42	12.580%	$55.637	$55.64	$55.65	$55.60
Purchase #3	$191.80	4.542%	$200.5116	$200.51	$200.50	$200.50
Purchase #4	$99.59	12.328%	$111.8675	$111.87	$111.85	$111.90
Purchase #5	$65.72	11.396%	$73.2095	$73.21	$73.20	$73.20
Purchase #6	$120.44	4.228%	$125.5322	$125.53	$125.55	$125.50
Purchase #7	$203.37	9.353%	$222.3912	$222.39	$222.40	$222.40
7 purchase totals =	$944.17		$1,020.3185	$1,020.32	$1,020.30	$1,020.30