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	$89.77	3.222%	$92.6624	$92.66	$92.65	$92.70
Purchase #2	$78.48	10.319%	$86.5784	$86.58	$86.60	$86.60
Purchase #3	$40.78	6.155%	$43.29	$43.29	$43.30	$43.30
Purchase #4	$47.91	13.624%	$54.4373	$54.44	$54.45	$54.40
Purchase #5	$80.98	13.745%	$92.1107	$92.11	$92.10	$92.10
Purchase #6	$68.57	13.496%	$77.8242	$77.82	$77.80	$77.80
Purchase #7	$35.42	10.411%	$39.1076	$39.11	$39.10	$39.10
7 purchase totals =	$441.91		$486.0106	$486.01	$486.00	$486.00