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	$133.90	9.121%	$146.113	$146.11	$146.10	$146.10
Purchase #2	$172.56	10.657%	$190.9497	$190.95	$190.95	$190.90
Purchase #3	$150.86	9.470%	$165.1464	$165.15	$165.15	$165.10
Purchase #4	$56.59	7.562%	$60.8693	$60.87	$60.85	$60.90
Purchase #5	$239.57	8.239%	$259.3082	$259.31	$259.30	$259.30
Purchase #6	$228.62	13.847%	$260.277	$260.28	$260.30	$260.30
Purchase #7	$214.76	7.821%	$231.5564	$231.56	$231.55	$231.60
7 purchase totals =	$1,196.86		$1,314.2200	$1,314.23	$1,314.20	$1,314.20