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	$72.94	12.550%	$82.094	$82.09	$82.10	$82.10
Purchase #2	$210.69	13.279%	$238.6675	$238.67	$238.65	$238.70
Purchase #3	$230.41	10.215%	$253.9464	$253.95	$253.95	$253.90
Purchase #4	$57.36	8.227%	$62.079	$62.08	$62.10	$62.10
Purchase #5	$23.53	11.675%	$26.2771	$26.28	$26.30	$26.30
Purchase #6	$187.68	13.739%	$213.4654	$213.47	$213.45	$213.50
Purchase #7	$190.89	7.333%	$204.888	$204.89	$204.90	$204.90
7 purchase totals =	$973.50		$1,081.4174	$1,081.43	$1,081.45	$1,081.50