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	$60.48	4.237%	$63.0425	$63.04	$63.05	$63.00
Purchase #2	$233.35	7.269%	$250.3122	$250.31	$250.30	$250.30
Purchase #3	$132.77	10.323%	$146.4758	$146.48	$146.50	$146.50
Purchase #4	$46.93	4.509%	$49.0461	$49.05	$49.05	$49.00
Purchase #5	$60.29	12.322%	$67.7189	$67.72	$67.70	$67.70
Purchase #6	$182.26	7.771%	$196.4234	$196.42	$196.40	$196.40
Purchase #7	$10.86	13.322%	$12.3068	$12.31	$12.30	$12.30
7 purchase totals =	$726.94		$785.3257	$785.33	$785.30	$785.20