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	$17.69	4.163%	$18.4264	$18.43	$18.45	$18.40
Purchase #2	$148.95	10.315%	$164.3142	$164.31	$164.30	$164.30
Purchase #3	$181.53	4.603%	$189.8858	$189.89	$189.90	$189.90
Purchase #4	$124.89	11.217%	$138.8989	$138.90	$138.90	$138.90
Purchase #5	$48.74	5.651%	$51.4943	$51.49	$51.50	$51.50
Purchase #6	$175.59	11.761%	$196.2411	$196.24	$196.25	$196.20
Purchase #7	$183.77	12.120%	$206.0429	$206.04	$206.05	$206.00
7 purchase totals =	$881.16		$965.3036	$965.30	$965.35	$965.20