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	$46.59	3.361%	$48.1559	$48.16	$48.15	$48.20
Purchase #2	$179.87	11.387%	$200.3518	$200.35	$200.35	$200.40
Purchase #3	$155.35	6.160%	$164.9196	$164.92	$164.90	$164.90
Purchase #4	$22.51	11.211%	$25.0336	$25.03	$25.05	$25.00
Purchase #5	$119.76	10.337%	$132.1396	$132.14	$132.15	$132.10
Purchase #6	$30.77	4.343%	$32.1063	$32.11	$32.10	$32.10
Purchase #7	$30.31	6.653%	$32.3265	$32.33	$32.35	$32.30
7 purchase totals =	$585.16		$635.0333	$635.04	$635.05	$635.00