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	$191.46	7.369%	$205.5687	$205.57	$205.55	$205.60
Purchase #2	$88.62	11.788%	$99.0665	$99.07	$99.05	$99.10
Purchase #3	$39.85	9.436%	$43.6102	$43.61	$43.60	$43.60
Purchase #4	$233.79	9.120%	$255.1116	$255.11	$255.10	$255.10
Purchase #5	$250.92	3.796%	$260.4449	$260.44	$260.45	$260.40
Purchase #6	$37.28	9.710%	$40.8999	$40.90	$40.90	$40.90
Purchase #7	$138.33	8.318%	$149.8363	$149.84	$149.85	$149.80
7 purchase totals =	$980.25		$1,054.5381	$1,054.54	$1,054.50	$1,054.50