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	$117.85	4.723%	$123.4161	$123.42	$123.40	$123.40
Purchase #2	$229.69	10.175%	$253.061	$253.06	$253.05	$253.10
Purchase #3	$100.62	11.308%	$111.9981	$112.00	$112.00	$112.00
Purchase #4	$147.73	13.392%	$167.514	$167.51	$167.50	$167.50
Purchase #5	$203.54	6.431%	$216.6297	$216.63	$216.65	$216.60
Purchase #6	$38.80	7.231%	$41.6056	$41.61	$41.60	$41.60
Purchase #7	$167.93	12.641%	$189.158	$189.16	$189.15	$189.20
7 purchase totals =	$1,006.16		$1,103.3825	$1,103.39	$1,103.35	$1,103.40