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	$176.92	7.409%	$190.028	$190.03	$190.05	$190.00
Purchase #2	$112.52	9.593%	$123.314	$123.31	$123.30	$123.30
Purchase #3	$132.45	11.254%	$147.3559	$147.36	$147.35	$147.40
Purchase #4	$166.98	13.262%	$189.1249	$189.12	$189.10	$189.10
Purchase #5	$140.67	12.795%	$158.6687	$158.67	$158.65	$158.70
Purchase #6	$38.48	8.640%	$41.8047	$41.80	$41.80	$41.80
Purchase #7	$147.96	9.610%	$162.179	$162.18	$162.20	$162.20
7 purchase totals =	$915.98		$1,012.4752	$1,012.47	$1,012.45	$1,012.50