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	$60.55	5.620%	$63.9529	$63.95	$63.95	$64.00
Purchase #2	$74.72	4.615%	$78.1683	$78.17	$78.15	$78.20
Purchase #3	$36.53	13.616%	$41.5039	$41.50	$41.50	$41.50
Purchase #4	$174.86	12.325%	$196.4115	$196.41	$196.40	$196.40
Purchase #5	$90.95	11.496%	$101.4056	$101.41	$101.40	$101.40
Purchase #6	$135.64	8.785%	$147.556	$147.56	$147.55	$147.60
Purchase #7	$54.64	12.348%	$61.3869	$61.39	$61.40	$61.40
7 purchase totals =	$627.89		$690.3851	$690.39	$690.35	$690.50