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	$37.94	13.665%	$43.1245	$43.12	$43.10	$43.10
Purchase #2	$94.58	11.388%	$105.3508	$105.35	$105.35	$105.40
Purchase #3	$114.59	9.520%	$125.499	$125.50	$125.50	$125.50
Purchase #4	$25.28	12.401%	$28.415	$28.42	$28.40	$28.40
Purchase #5	$183.58	4.611%	$192.0449	$192.04	$192.05	$192.00
Purchase #6	$141.31	4.333%	$147.433	$147.43	$147.45	$147.40
Purchase #7	$63.93	11.606%	$71.3497	$71.35	$71.35	$71.30
7 purchase totals =	$661.21		$713.2169	$713.21	$713.20	$713.10