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	$226.44	3.283%	$233.874	$233.87	$233.85	$233.90
Purchase #2	$210.96	12.275%	$236.8553	$236.86	$236.85	$236.90
Purchase #3	$134.36	10.589%	$148.5874	$148.59	$148.60	$148.60
Purchase #4	$173.84	8.852%	$189.2283	$189.23	$189.25	$189.20
Purchase #5	$97.66	6.821%	$104.3214	$104.32	$104.30	$104.30
Purchase #6	$247.91	5.408%	$261.317	$261.32	$261.30	$261.30
Purchase #7	$55.65	6.390%	$59.206	$59.21	$59.20	$59.20
7 purchase totals =	$1,146.82		$1,233.3894	$1,233.40	$1,233.35	$1,233.40