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	$169.96	11.220%	$189.0295	$189.03	$189.05	$189.00
Purchase #2	$61.87	4.467%	$64.6337	$64.63	$64.65	$64.60
Purchase #3	$33.86	11.849%	$37.8721	$37.87	$37.85	$37.90
Purchase #4	$106.45	4.806%	$111.566	$111.57	$111.55	$111.60
Purchase #5	$244.94	3.487%	$253.4811	$253.48	$253.50	$253.50
Purchase #6	$218.55	3.526%	$226.2561	$226.26	$226.25	$226.30
Purchase #7	$115.84	12.796%	$130.6629	$130.66	$130.65	$130.70
7 purchase totals =	$951.47		$1,013.5014	$1,013.50	$1,013.50	$1,013.60