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	$215.73	11.406%	$240.3362	$240.34	$240.35	$240.30
Purchase #2	$218.40	9.104%	$238.2831	$238.28	$238.30	$238.30
Purchase #3	$46.98	7.787%	$50.6383	$50.64	$50.65	$50.60
Purchase #4	$223.66	6.560%	$238.3321	$238.33	$238.35	$238.30
Purchase #5	$47.73	9.513%	$52.2706	$52.27	$52.25	$52.30
Purchase #6	$118.53	7.530%	$127.4553	$127.46	$127.45	$127.50
Purchase #7	$15.73	3.810%	$16.3293	$16.33	$16.35	$16.30
7 purchase totals =	$886.76		$963.6449	$963.65	$963.70	$963.60