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	$88.83	3.159%	$91.6361	$91.64	$91.65	$91.60
Purchase #2	$215.44	10.732%	$238.561	$238.56	$238.55	$238.60
Purchase #3	$45.70	10.147%	$50.3372	$50.34	$50.35	$50.30
Purchase #4	$232.73	8.822%	$253.2614	$253.26	$253.25	$253.30
Purchase #5	$123.86	6.518%	$131.9332	$131.93	$131.95	$131.90
Purchase #6	$149.43	13.674%	$169.8631	$169.86	$169.85	$169.90
Purchase #7	$210.52	9.804%	$231.1594	$231.16	$231.15	$231.20
7 purchase totals =	$1,066.51		$1,166.7514	$1,166.75	$1,166.75	$1,166.80