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	$28.75	13.229%	$32.5533	$32.55	$32.55	$32.60
Purchase #2	$54.77	3.282%	$56.5676	$56.57	$56.55	$56.60
Purchase #3	$92.69	8.574%	$100.6372	$100.64	$100.65	$100.60
Purchase #4	$27.35	13.496%	$31.0412	$31.04	$31.05	$31.00
Purchase #5	$169.69	3.190%	$175.1031	$175.10	$175.10	$175.10
Purchase #6	$247.76	6.486%	$263.8297	$263.83	$263.85	$263.80
Purchase #7	$146.58	4.241%	$152.7965	$152.80	$152.80	$152.80
7 purchase totals =	$767.59		$812.5286	$812.53	$812.55	$812.50