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	$40.28	12.799%	$45.4354	$45.44	$45.45	$45.40
Purchase #2	$190.87	7.166%	$204.5477	$204.55	$204.55	$204.50
Purchase #3	$52.31	5.550%	$55.2132	$55.21	$55.20	$55.20
Purchase #4	$224.83	13.403%	$254.964	$254.96	$254.95	$255.00
Purchase #5	$134.30	5.234%	$141.3293	$141.33	$141.35	$141.30
Purchase #6	$70.96	12.583%	$79.8889	$79.89	$79.90	$79.90
Purchase #7	$100.88	12.230%	$113.2176	$113.22	$113.20	$113.20
7 purchase totals =	$814.43		$894.5961	$894.60	$894.60	$894.50