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	$78.62	4.608%	$82.2428	$82.24	$82.25	$82.20
Purchase #2	$123.30	11.435%	$137.3994	$137.40	$137.40	$137.40
Purchase #3	$150.63	5.652%	$159.1436	$159.14	$159.15	$159.10
Purchase #4	$82.72	3.626%	$85.7194	$85.72	$85.70	$85.70
Purchase #5	$139.31	11.250%	$154.9824	$154.98	$155.00	$155.00
Purchase #6	$21.70	3.564%	$22.4734	$22.47	$22.45	$22.50
Purchase #7	$238.81	9.776%	$262.1561	$262.16	$262.15	$262.20
7 purchase totals =	$835.09		$904.1171	$904.11	$904.10	$904.10