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	$9.41	7.785%	$10.1426	$10.14	$10.15	$10.10
Purchase #2	$204.75	4.630%	$214.2299	$214.23	$214.25	$214.20
Purchase #3	$205.61	11.465%	$229.1832	$229.18	$229.20	$229.20
Purchase #4	$204.32	4.417%	$213.3448	$213.34	$213.35	$213.30
Purchase #5	$166.65	13.635%	$189.3727	$189.37	$189.35	$189.40
Purchase #6	$66.94	8.224%	$72.4451	$72.45	$72.45	$72.40
Purchase #7	$147.27	3.171%	$151.9399	$151.94	$151.95	$151.90
7 purchase totals =	$1,004.95		$1,080.6582	$1,080.65	$1,080.70	$1,080.50