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	$114.25	8.549%	$124.0172	$124.02	$124.00	$124.00
Purchase #2	$22.70	3.450%	$23.4832	$23.48	$23.50	$23.50
Purchase #3	$37.72	10.547%	$41.6983	$41.70	$41.70	$41.70
Purchase #4	$81.81	12.214%	$91.8023	$91.80	$91.80	$91.80
Purchase #5	$76.31	7.649%	$82.147	$82.15	$82.15	$82.10
Purchase #6	$40.77	3.712%	$42.2834	$42.28	$42.30	$42.30
Purchase #7	$96.71	4.144%	$100.7177	$100.72	$100.70	$100.70
7 purchase totals =	$470.27		$506.1491	$506.15	$506.15	$506.10