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	$126.87	12.872%	$143.2007	$143.20	$143.20	$143.20
Purchase #2	$83.85	10.820%	$92.9226	$92.92	$92.90	$92.90
Purchase #3	$189.76	5.583%	$200.3543	$200.35	$200.35	$200.40
Purchase #4	$22.71	11.779%	$25.385	$25.39	$25.40	$25.40
Purchase #5	$130.41	9.142%	$142.3321	$142.33	$142.35	$142.30
Purchase #6	$232.41	11.151%	$258.326	$258.33	$258.35	$258.30
Purchase #7	$200.88	9.492%	$219.9475	$219.95	$219.95	$219.90
7 purchase totals =	$986.89		$1,082.4682	$1,082.47	$1,082.50	$1,082.40