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	$124.57	10.506%	$137.6573	$137.66	$137.65	$137.70
Purchase #2	$95.96	7.469%	$103.1273	$103.13	$103.15	$103.10
Purchase #3	$148.93	7.618%	$160.2755	$160.28	$160.30	$160.30
Purchase #4	$173.89	10.136%	$191.5155	$191.52	$191.50	$191.50
Purchase #5	$132.34	11.108%	$147.0403	$147.04	$147.05	$147.00
Purchase #6	$216.71	3.366%	$224.0045	$224.00	$224.00	$224.00
Purchase #7	$128.61	6.313%	$136.7291	$136.73	$136.75	$136.70
7 purchase totals =	$1,021.01		$1,100.3495	$1,100.36	$1,100.40	$1,100.30