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	$76.71	11.228%	$85.323	$85.32	$85.30	$85.30
Purchase #2	$35.71	5.590%	$37.7062	$37.71	$37.70	$37.70
Purchase #3	$148.51	12.572%	$167.1807	$167.18	$167.20	$167.20
Purchase #4	$86.66	4.560%	$90.6117	$90.61	$90.60	$90.60
Purchase #5	$228.85	6.610%	$243.977	$243.98	$244.00	$244.00
Purchase #6	$234.87	12.350%	$263.8764	$263.88	$263.90	$263.90
Purchase #7	$230.55	4.601%	$241.1576	$241.16	$241.15	$241.20
7 purchase totals =	$1,041.86		$1,129.8326	$1,129.84	$1,129.85	$1,129.90