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	$61.72	9.426%	$67.5377	$67.54	$67.55	$67.50
Purchase #2	$80.82	3.347%	$83.525	$83.53	$83.55	$83.50
Purchase #3	$55.83	6.128%	$59.2513	$59.25	$59.25	$59.30
Purchase #4	$186.46	9.275%	$203.7542	$203.75	$203.75	$203.80
Purchase #5	$180.34	5.377%	$190.0369	$190.04	$190.05	$190.00
Purchase #6	$200.82	5.268%	$211.3992	$211.40	$211.40	$211.40
Purchase #7	$147.76	11.780%	$165.1661	$165.17	$165.15	$165.20
7 purchase totals =	$913.75		$980.6704	$980.68	$980.70	$980.70