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	$166.33	5.325%	$175.1871	$175.19	$175.20	$175.20
Purchase #2	$214.45	5.140%	$225.4727	$225.47	$225.45	$225.50
Purchase #3	$95.33	11.662%	$106.4474	$106.45	$106.45	$106.40
Purchase #4	$201.48	4.221%	$209.9845	$209.98	$210.00	$210.00
Purchase #5	$78.36	13.779%	$89.1572	$89.16	$89.15	$89.20
Purchase #6	$156.87	7.486%	$168.6133	$168.61	$168.60	$168.60
Purchase #7	$186.30	5.362%	$196.2894	$196.29	$196.30	$196.30
7 purchase totals =	$1,099.12		$1,171.1516	$1,171.15	$1,171.15	$1,171.20