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	$74.36	10.872%	$82.4444	$82.44	$82.45	$82.40
Purchase #2	$32.33	11.745%	$36.1272	$36.13	$36.15	$36.10
Purchase #3	$209.70	13.485%	$237.978	$237.98	$238.00	$238.00
Purchase #4	$109.43	13.748%	$124.4744	$124.47	$124.45	$124.50
Purchase #5	$175.67	8.516%	$190.6301	$190.63	$190.65	$190.60
Purchase #6	$169.30	12.710%	$190.818	$190.82	$190.80	$190.80
Purchase #7	$215.35	6.250%	$228.8094	$228.81	$228.80	$228.80
7 purchase totals =	$986.14		$1,091.2815	$1,091.28	$1,091.30	$1,091.20