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	$160.80	7.495%	$172.852	$172.85	$172.85	$172.90
Purchase #2	$245.33	13.150%	$277.5909	$277.59	$277.60	$277.60
Purchase #3	$86.53	8.869%	$94.2043	$94.20	$94.20	$94.20
Purchase #4	$249.53	5.758%	$263.8979	$263.90	$263.90	$263.90
Purchase #5	$101.50	8.529%	$110.1569	$110.16	$110.15	$110.20
Purchase #6	$249.50	8.793%	$271.4385	$271.44	$271.45	$271.40
Purchase #7	$57.86	12.612%	$65.1573	$65.16	$65.15	$65.20
7 purchase totals =	$1,151.05		$1,255.2978	$1,255.30	$1,255.30	$1,255.40