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	$189.90	3.406%	$196.368	$196.37	$196.35	$196.40
Purchase #2	$83.95	13.829%	$95.5594	$95.56	$95.55	$95.60
Purchase #3	$13.76	6.717%	$14.6843	$14.68	$14.70	$14.70
Purchase #4	$81.46	11.371%	$90.7228	$90.72	$90.70	$90.70
Purchase #5	$240.44	13.618%	$273.1831	$273.18	$273.20	$273.20
Purchase #6	$43.40	13.511%	$49.2638	$49.26	$49.25	$49.30
Purchase #7	$172.87	7.120%	$185.1783	$185.18	$185.20	$185.20
7 purchase totals =	$825.78		$904.9597	$904.95	$904.95	$905.10