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	$10.44	4.677%	$10.9283	$10.93	$10.95	$10.90
Purchase #2	$125.52	13.654%	$142.6585	$142.66	$142.65	$142.70
Purchase #3	$137.79	9.207%	$150.4763	$150.48	$150.50	$150.50
Purchase #4	$42.98	8.415%	$46.5968	$46.60	$46.60	$46.60
Purchase #5	$232.74	9.822%	$255.5997	$255.60	$255.60	$255.60
Purchase #6	$60.65	8.198%	$65.6221	$65.62	$65.60	$65.60
Purchase #7	$76.34	6.727%	$81.4754	$81.48	$81.50	$81.50
7 purchase totals =	$686.46		$753.3571	$753.37	$753.40	$753.40