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	$185.96	4.143%	$193.6643	$193.66	$193.65	$193.70
Purchase #2	$37.83	12.754%	$42.6548	$42.65	$42.65	$42.70
Purchase #3	$220.88	4.184%	$230.1216	$230.12	$230.10	$230.10
Purchase #4	$151.91	4.503%	$158.7505	$158.75	$158.75	$158.80
Purchase #5	$225.77	9.682%	$247.6291	$247.63	$247.65	$247.60
Purchase #6	$188.98	4.183%	$196.885	$196.89	$196.90	$196.90
Purchase #7	$163.31	12.420%	$183.5931	$183.59	$183.60	$183.60
7 purchase totals =	$1,174.64		$1,253.2984	$1,253.29	$1,253.30	$1,253.40