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	$130.53	5.557%	$137.7836	$137.78	$137.80	$137.80
Purchase #2	$195.54	12.804%	$220.5769	$220.58	$220.60	$220.60
Purchase #3	$215.96	12.280%	$242.4799	$242.48	$242.50	$242.50
Purchase #4	$147.77	12.147%	$165.7196	$165.72	$165.70	$165.70
Purchase #5	$162.51	8.137%	$175.7334	$175.73	$175.75	$175.70
Purchase #6	$59.35	4.346%	$61.9294	$61.93	$61.95	$61.90
Purchase #7	$137.81	3.225%	$142.2544	$142.25	$142.25	$142.30
7 purchase totals =	$1,049.47		$1,146.4772	$1,146.47	$1,146.55	$1,146.50