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	$154.32	7.331%	$165.6332	$165.63	$165.65	$165.60
Purchase #2	$174.65	6.761%	$186.4581	$186.46	$186.45	$186.50
Purchase #3	$174.67	4.185%	$181.9799	$181.98	$182.00	$182.00
Purchase #4	$246.91	11.301%	$274.8133	$274.81	$274.80	$274.80
Purchase #5	$130.57	7.408%	$140.2426	$140.24	$140.25	$140.20
Purchase #6	$33.99	11.464%	$37.8866	$37.89	$37.90	$37.90
Purchase #7	$18.86	12.848%	$21.2831	$21.28	$21.30	$21.30
7 purchase totals =	$933.97		$1,008.2968	$1,008.29	$1,008.35	$1,008.30