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	$131.42	8.452%	$142.5276	$142.53	$142.55	$142.50
Purchase #2	$170.60	8.756%	$185.5377	$185.54	$185.55	$185.50
Purchase #3	$224.71	6.282%	$238.8263	$238.83	$238.85	$238.80
Purchase #4	$21.84	7.132%	$23.3976	$23.40	$23.40	$23.40
Purchase #5	$15.98	8.474%	$17.3341	$17.33	$17.35	$17.30
Purchase #6	$215.50	13.639%	$244.892	$244.89	$244.90	$244.90
Purchase #7	$179.57	11.460%	$200.1487	$200.15	$200.15	$200.10
7 purchase totals =	$959.62		$1,052.6640	$1,052.67	$1,052.75	$1,052.50