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	$130.93	11.387%	$145.839	$145.84	$145.85	$145.80
Purchase #2	$225.32	8.451%	$244.3618	$244.36	$244.35	$244.40
Purchase #3	$78.98	12.678%	$88.9931	$88.99	$89.00	$89.00
Purchase #4	$50.60	9.344%	$55.3281	$55.33	$55.35	$55.30
Purchase #5	$52.90	3.334%	$54.6637	$54.66	$54.65	$54.70
Purchase #6	$32.64	13.320%	$36.9876	$36.99	$37.00	$37.00
Purchase #7	$95.51	4.283%	$99.6007	$99.60	$99.60	$99.60
7 purchase totals =	$666.88		$725.7740	$725.77	$725.80	$725.80