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	$42.45	6.758%	$45.3188	$45.32	$45.30	$45.30
Purchase #2	$138.72	7.798%	$149.5374	$149.54	$149.55	$149.50
Purchase #3	$188.73	6.229%	$200.486	$200.49	$200.50	$200.50
Purchase #4	$175.79	3.499%	$181.9409	$181.94	$181.95	$181.90
Purchase #5	$33.41	6.282%	$35.5088	$35.51	$35.50	$35.50
Purchase #6	$203.59	13.718%	$231.5185	$231.52	$231.50	$231.50
Purchase #7	$242.77	6.208%	$257.8412	$257.84	$257.85	$257.80
7 purchase totals =	$1,025.46		$1,102.1516	$1,102.16	$1,102.15	$1,102.00