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	$235.82	12.602%	$265.538	$265.54	$265.55	$265.50
Purchase #2	$101.40	9.830%	$111.3676	$111.37	$111.35	$111.40
Purchase #3	$164.52	11.217%	$182.9742	$182.97	$182.95	$183.00
Purchase #4	$95.25	11.742%	$106.4343	$106.43	$106.45	$106.40
Purchase #5	$198.94	13.320%	$225.4388	$225.44	$225.45	$225.40
Purchase #6	$60.50	12.837%	$68.2664	$68.27	$68.25	$68.30
Purchase #7	$179.53	9.334%	$196.2873	$196.29	$196.30	$196.30
7 purchase totals =	$1,035.96		$1,156.3066	$1,156.31	$1,156.30	$1,156.30