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	$173.87	11.126%	$193.2148	$193.21	$193.20	$193.20
Purchase #2	$203.64	10.805%	$225.6433	$225.64	$225.65	$225.60
Purchase #3	$171.78	10.570%	$189.9371	$189.94	$189.95	$189.90
Purchase #4	$182.42	4.343%	$190.3425	$190.34	$190.35	$190.30
Purchase #5	$221.53	5.236%	$233.1293	$233.13	$233.15	$233.10
Purchase #6	$196.75	13.730%	$223.7638	$223.76	$223.75	$223.80
Purchase #7	$7.31	3.394%	$7.5581	$7.56	$7.55	$7.60
7 purchase totals =	$1,157.30		$1,263.5889	$1,263.58	$1,263.60	$1,263.50