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	$76.31	8.331%	$82.6674	$82.67	$82.65	$82.70
Purchase #2	$213.34	7.421%	$229.172	$229.17	$229.15	$229.20
Purchase #3	$210.96	11.208%	$234.6044	$234.60	$234.60	$234.60
Purchase #4	$102.77	8.821%	$111.8353	$111.84	$111.85	$111.80
Purchase #5	$91.93	13.635%	$104.4647	$104.46	$104.45	$104.50
Purchase #6	$99.40	6.616%	$105.9763	$105.98	$106.00	$106.00
Purchase #7	$112.91	11.430%	$125.8156	$125.82	$125.80	$125.80
7 purchase totals =	$907.62		$994.5357	$994.54	$994.50	$994.60