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	$135.62	12.412%	$152.4532	$152.45	$152.45	$152.50
Purchase #2	$37.37	8.493%	$40.5438	$40.54	$40.55	$40.50
Purchase #3	$89.33	5.516%	$94.2574	$94.26	$94.25	$94.30
Purchase #4	$44.49	7.333%	$47.7525	$47.75	$47.75	$47.80
Purchase #5	$223.32	11.435%	$248.8566	$248.86	$248.85	$248.90
Purchase #6	$210.91	11.121%	$234.3653	$234.37	$234.35	$234.40
Purchase #7	$246.43	3.452%	$254.9368	$254.94	$254.95	$254.90
7 purchase totals =	$987.47		$1,073.1656	$1,073.17	$1,073.15	$1,073.30