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	$172.62	13.589%	$196.0773	$196.08	$196.10	$196.10
Purchase #2	$100.38	4.517%	$104.9142	$104.91	$104.90	$104.90
Purchase #3	$66.91	5.727%	$70.7419	$70.74	$70.75	$70.70
Purchase #4	$61.50	6.488%	$65.4901	$65.49	$65.50	$65.50
Purchase #5	$53.65	5.790%	$56.7563	$56.76	$56.75	$56.80
Purchase #6	$203.46	12.343%	$228.5731	$228.57	$228.55	$228.60
Purchase #7	$126.66	12.507%	$142.5014	$142.50	$142.50	$142.50
7 purchase totals =	$785.18		$865.0543	$865.05	$865.05	$865.10