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	$87.50	3.602%	$90.6518	$90.65	$90.65	$90.70
Purchase #2	$218.25	4.482%	$228.032	$228.03	$228.05	$228.00
Purchase #3	$153.83	7.412%	$165.2319	$165.23	$165.25	$165.20
Purchase #4	$246.31	10.489%	$272.1455	$272.15	$272.15	$272.10
Purchase #5	$132.47	13.424%	$150.2528	$150.25	$150.25	$150.30
Purchase #6	$96.50	12.636%	$108.6937	$108.69	$108.70	$108.70
Purchase #7	$154.51	8.297%	$167.3297	$167.33	$167.35	$167.30
7 purchase totals =	$1,089.37		$1,182.3374	$1,182.33	$1,182.40	$1,182.30