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	$141.92	11.648%	$158.4508	$158.45	$158.45	$158.50
Purchase #2	$148.98	7.291%	$159.8421	$159.84	$159.85	$159.80
Purchase #3	$135.56	4.184%	$141.2318	$141.23	$141.25	$141.20
Purchase #4	$170.54	11.632%	$190.3772	$190.38	$190.40	$190.40
Purchase #5	$16.63	8.340%	$18.0169	$18.02	$18.00	$18.00
Purchase #6	$122.34	12.421%	$137.5359	$137.54	$137.55	$137.50
Purchase #7	$191.30	8.158%	$206.9063	$206.91	$206.90	$206.90
7 purchase totals =	$927.27		$1,012.3610	$1,012.37	$1,012.40	$1,012.30