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	$177.77	10.529%	$196.4874	$196.49	$196.50	$196.50
Purchase #2	$139.96	9.343%	$153.0365	$153.04	$153.05	$153.00
Purchase #3	$191.40	7.140%	$205.066	$205.07	$205.05	$205.10
Purchase #4	$63.70	5.512%	$67.2111	$67.21	$67.20	$67.20
Purchase #5	$135.75	4.313%	$141.6049	$141.60	$141.60	$141.60
Purchase #6	$81.42	13.392%	$92.3238	$92.32	$92.30	$92.30
Purchase #7	$138.83	6.512%	$147.8706	$147.87	$147.85	$147.90
7 purchase totals =	$928.83		$1,003.6003	$1,003.60	$1,003.55	$1,003.60