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	$147.82	11.296%	$164.5177	$164.52	$164.50	$164.50
Purchase #2	$85.80	6.377%	$91.2715	$91.27	$91.25	$91.30
Purchase #3	$105.90	6.733%	$113.0302	$113.03	$113.05	$113.00
Purchase #4	$230.68	10.562%	$255.0444	$255.04	$255.05	$255.00
Purchase #5	$182.92	12.736%	$206.2167	$206.22	$206.20	$206.20
Purchase #6	$151.55	12.421%	$170.374	$170.37	$170.35	$170.40
Purchase #7	$225.38	12.316%	$253.1378	$253.14	$253.15	$253.10
7 purchase totals =	$1,130.05		$1,253.5923	$1,253.59	$1,253.55	$1,253.50