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	$155.78	4.472%	$162.7465	$162.75	$162.75	$162.70
Purchase #2	$116.72	6.160%	$123.91	$123.91	$123.90	$123.90
Purchase #3	$224.25	5.530%	$236.651	$236.65	$236.65	$236.70
Purchase #4	$230.84	9.650%	$253.1161	$253.12	$253.10	$253.10
Purchase #5	$107.25	5.467%	$113.1134	$113.11	$113.10	$113.10
Purchase #6	$152.62	10.245%	$168.2559	$168.26	$168.25	$168.30
Purchase #7	$104.56	8.637%	$113.5908	$113.59	$113.60	$113.60
7 purchase totals =	$1,092.02		$1,171.3837	$1,171.39	$1,171.35	$1,171.40