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	$238.89	3.750%	$247.8484	$247.85	$247.85	$247.80
Purchase #2	$130.75	10.256%	$144.1597	$144.16	$144.15	$144.20
Purchase #3	$79.91	6.313%	$84.9547	$84.95	$84.95	$85.00
Purchase #4	$25.33	12.479%	$28.4909	$28.49	$28.50	$28.50
Purchase #5	$87.57	9.705%	$96.0687	$96.07	$96.05	$96.10
Purchase #6	$170.42	10.853%	$188.9157	$188.92	$188.90	$188.90
Purchase #7	$179.91	3.171%	$185.6149	$185.61	$185.60	$185.60
7 purchase totals =	$912.78		$976.0530	$976.05	$976.00	$976.10