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	$172.88	13.867%	$196.8533	$196.85	$196.85	$196.90
Purchase #2	$210.39	7.275%	$225.6959	$225.70	$225.70	$225.70
Purchase #3	$187.78	5.395%	$197.9107	$197.91	$197.90	$197.90
Purchase #4	$81.36	10.796%	$90.1436	$90.14	$90.15	$90.10
Purchase #5	$123.65	7.630%	$133.0845	$133.08	$133.10	$133.10
Purchase #6	$48.80	10.800%	$54.0704	$54.07	$54.05	$54.10
Purchase #7	$30.32	8.467%	$32.8872	$32.89	$32.90	$32.90
7 purchase totals =	$855.18		$930.6456	$930.64	$930.65	$930.70