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	$64.89	3.769%	$67.3357	$67.34	$67.35	$67.30
Purchase #2	$81.72	10.537%	$90.3308	$90.33	$90.35	$90.30
Purchase #3	$19.96	11.422%	$22.2398	$22.24	$22.25	$22.20
Purchase #4	$249.88	4.761%	$261.7768	$261.78	$261.80	$261.80
Purchase #5	$100.69	4.402%	$105.1224	$105.12	$105.10	$105.10
Purchase #6	$142.26	5.580%	$150.1981	$150.20	$150.20	$150.20
Purchase #7	$205.38	13.307%	$232.7099	$232.71	$232.70	$232.70
7 purchase totals =	$864.78		$929.7135	$929.72	$929.75	$929.60