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	$202.43	7.718%	$218.0535	$218.05	$218.05	$218.10
Purchase #2	$132.48	13.790%	$150.749	$150.75	$150.75	$150.70
Purchase #3	$40.48	5.699%	$42.787	$42.79	$42.80	$42.80
Purchase #4	$86.99	4.342%	$90.7671	$90.77	$90.75	$90.80
Purchase #5	$21.30	3.451%	$22.0351	$22.04	$22.05	$22.00
Purchase #6	$185.80	9.852%	$204.105	$204.11	$204.10	$204.10
Purchase #7	$61.92	9.682%	$67.9151	$67.92	$67.90	$67.90
7 purchase totals =	$731.40		$796.4118	$796.43	$796.40	$796.40