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	$186.66	12.223%	$209.4755	$209.48	$209.50	$209.50
Purchase #2	$83.57	3.476%	$86.4749	$86.47	$86.45	$86.50
Purchase #3	$246.68	12.418%	$277.3127	$277.31	$277.30	$277.30
Purchase #4	$153.64	3.769%	$159.4307	$159.43	$159.45	$159.40
Purchase #5	$158.48	4.484%	$165.5862	$165.59	$165.60	$165.60
Purchase #6	$138.43	5.522%	$146.0741	$146.07	$146.05	$146.10
Purchase #7	$90.30	10.604%	$99.8754	$99.88	$99.90	$99.90
7 purchase totals =	$1,057.76		$1,144.2295	$1,144.23	$1,144.25	$1,144.30