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	$69.83	4.409%	$72.9088	$72.91	$72.90	$72.90
Purchase #2	$243.41	12.756%	$274.4594	$274.46	$274.45	$274.50
Purchase #3	$63.51	5.525%	$67.0189	$67.02	$67.00	$67.00
Purchase #4	$11.38	8.655%	$12.3649	$12.36	$12.35	$12.40
Purchase #5	$66.38	9.668%	$72.7976	$72.80	$72.80	$72.80
Purchase #6	$155.30	6.303%	$165.0886	$165.09	$165.10	$165.10
Purchase #7	$233.40	11.728%	$260.7732	$260.77	$260.75	$260.80
7 purchase totals =	$843.21		$925.4114	$925.41	$925.35	$925.50