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	$96.91	12.414%	$108.9404	$108.94	$108.95	$108.90
Purchase #2	$86.89	11.143%	$96.5722	$96.57	$96.55	$96.60
Purchase #3	$18.74	10.822%	$20.768	$20.77	$20.75	$20.80
Purchase #4	$82.31	3.624%	$85.2929	$85.29	$85.30	$85.30
Purchase #5	$161.61	10.669%	$178.8522	$178.85	$178.85	$178.90
Purchase #6	$198.60	11.501%	$221.441	$221.44	$221.45	$221.40
Purchase #7	$208.43	7.306%	$223.6579	$223.66	$223.65	$223.70
7 purchase totals =	$853.49		$935.5246	$935.52	$935.50	$935.60