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	$35.53	4.130%	$36.9974	$37.00	$37.00	$37.00
Purchase #2	$137.66	12.109%	$154.3292	$154.33	$154.35	$154.30
Purchase #3	$53.87	5.586%	$56.8792	$56.88	$56.90	$56.90
Purchase #4	$168.83	4.676%	$176.7245	$176.72	$176.70	$176.70
Purchase #5	$53.57	8.862%	$58.3174	$58.32	$58.30	$58.30
Purchase #6	$170.34	10.820%	$188.7708	$188.77	$188.75	$188.80
Purchase #7	$37.71	12.641%	$42.4769	$42.48	$42.50	$42.50
7 purchase totals =	$657.51		$714.4954	$714.50	$714.50	$714.50