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	$220.67	6.116%	$234.1662	$234.17	$234.15	$234.20
Purchase #2	$84.47	5.462%	$89.0838	$89.08	$89.10	$89.10
Purchase #3	$92.92	6.675%	$99.1224	$99.12	$99.10	$99.10
Purchase #4	$55.91	12.535%	$62.9183	$62.92	$62.90	$62.90
Purchase #5	$235.25	5.687%	$248.6287	$248.63	$248.65	$248.60
Purchase #6	$70.61	10.741%	$78.1942	$78.19	$78.20	$78.20
Purchase #7	$135.47	11.201%	$150.644	$150.64	$150.65	$150.60
7 purchase totals =	$895.30		$962.7576	$962.75	$962.75	$962.70