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	$92.60	13.513%	$105.113	$105.11	$105.10	$105.10
Purchase #2	$87.38	5.794%	$92.4428	$92.44	$92.45	$92.40
Purchase #3	$129.33	9.322%	$141.3861	$141.39	$141.40	$141.40
Purchase #4	$77.47	10.750%	$85.798	$85.80	$85.80	$85.80
Purchase #5	$173.67	3.108%	$179.0677	$179.07	$179.05	$179.10
Purchase #6	$110.73	7.163%	$118.6616	$118.66	$118.65	$118.70
Purchase #7	$246.49	13.654%	$280.1457	$280.15	$280.15	$280.10
7 purchase totals =	$917.67		$1,002.6149	$1,002.62	$1,002.60	$1,002.60