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	$51.92	5.229%	$54.6349	$54.63	$54.65	$54.60
Purchase #2	$126.75	7.742%	$136.563	$136.56	$136.55	$136.60
Purchase #3	$212.38	4.817%	$222.6103	$222.61	$222.60	$222.60
Purchase #4	$87.32	9.616%	$95.7167	$95.72	$95.70	$95.70
Purchase #5	$97.74	11.456%	$108.9371	$108.94	$108.95	$108.90
Purchase #6	$145.46	5.557%	$153.5432	$153.54	$153.55	$153.50
Purchase #7	$84.44	10.851%	$93.6026	$93.60	$93.60	$93.60
7 purchase totals =	$806.01		$865.6078	$865.60	$865.60	$865.50