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	$222.55	10.616%	$246.1759	$246.18	$246.20	$246.20
Purchase #2	$76.68	7.328%	$82.2991	$82.30	$82.30	$82.30
Purchase #3	$196.65	4.104%	$204.7205	$204.72	$204.70	$204.70
Purchase #4	$199.47	8.592%	$216.6085	$216.61	$216.60	$216.60
Purchase #5	$73.63	11.753%	$82.2837	$82.28	$82.30	$82.30
Purchase #6	$12.29	3.598%	$12.7322	$12.73	$12.75	$12.70
Purchase #7	$174.95	6.284%	$185.9439	$185.94	$185.95	$185.90
7 purchase totals =	$956.22		$1,030.7638	$1,030.76	$1,030.80	$1,030.70