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	$176.41	13.713%	$200.6011	$200.60	$200.60	$200.60
Purchase #2	$160.27	3.444%	$165.7897	$165.79	$165.80	$165.80
Purchase #3	$74.85	11.712%	$83.6164	$83.62	$83.60	$83.60
Purchase #4	$139.50	13.644%	$158.5334	$158.53	$158.55	$158.50
Purchase #5	$168.90	12.688%	$190.33	$190.33	$190.35	$190.30
Purchase #6	$121.53	6.501%	$129.4307	$129.43	$129.45	$129.40
Purchase #7	$241.66	3.433%	$249.9562	$249.96	$249.95	$250.00
7 purchase totals =	$1,083.12		$1,178.2575	$1,178.26	$1,178.30	$1,178.20