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	$190.39	4.722%	$199.3802	$199.38	$199.40	$199.40
Purchase #2	$235.95	8.125%	$255.1209	$255.12	$255.10	$255.10
Purchase #3	$158.48	6.169%	$168.2566	$168.26	$168.25	$168.30
Purchase #4	$183.35	3.722%	$190.1743	$190.17	$190.15	$190.20
Purchase #5	$83.49	7.486%	$89.7401	$89.74	$89.75	$89.70
Purchase #6	$42.37	4.740%	$44.3783	$44.38	$44.40	$44.40
Purchase #7	$206.46	7.118%	$221.1558	$221.16	$221.15	$221.20
7 purchase totals =	$1,100.49		$1,168.2062	$1,168.21	$1,168.20	$1,168.30