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	$119.41	10.302%	$131.7116	$131.71	$131.70	$131.70
Purchase #2	$173.36	4.515%	$181.1872	$181.19	$181.20	$181.20
Purchase #3	$34.91	8.578%	$37.9046	$37.90	$37.90	$37.90
Purchase #4	$144.54	7.419%	$155.2634	$155.26	$155.25	$155.30
Purchase #5	$126.59	10.106%	$139.3832	$139.38	$139.40	$139.40
Purchase #6	$87.69	4.411%	$91.558	$91.56	$91.55	$91.60
Purchase #7	$124.94	4.282%	$130.2899	$130.29	$130.30	$130.30
7 purchase totals =	$811.44		$867.2979	$867.29	$867.30	$867.40