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	$83.98	8.258%	$90.9151	$90.92	$90.90	$90.90
Purchase #2	$247.49	11.310%	$275.4811	$275.48	$275.50	$275.50
Purchase #3	$234.57	4.235%	$244.504	$244.50	$244.50	$244.50
Purchase #4	$146.49	10.605%	$162.0253	$162.03	$162.05	$162.00
Purchase #5	$8.62	10.427%	$9.5188	$9.52	$9.50	$9.50
Purchase #6	$190.97	4.481%	$199.5274	$199.53	$199.55	$199.50
Purchase #7	$69.54	3.186%	$71.7555	$71.76	$71.75	$71.80
7 purchase totals =	$981.66		$1,053.7272	$1,053.74	$1,053.75	$1,053.70