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	$222.59	5.229%	$234.2292	$234.23	$234.25	$234.20
Purchase #2	$59.49	5.602%	$62.8226	$62.82	$62.80	$62.80
Purchase #3	$144.75	5.166%	$152.2278	$152.23	$152.25	$152.20
Purchase #4	$172.86	9.194%	$188.7527	$188.75	$188.75	$188.80
Purchase #5	$116.94	11.839%	$130.7845	$130.78	$130.80	$130.80
Purchase #6	$211.59	9.664%	$232.0381	$232.04	$232.05	$232.00
Purchase #7	$178.78	6.748%	$190.8441	$190.84	$190.85	$190.80
7 purchase totals =	$1,107.00		$1,191.6990	$1,191.69	$1,191.75	$1,191.60