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	$200.56	4.532%	$209.6494	$209.65	$209.65	$209.60
Purchase #2	$125.57	4.620%	$131.3713	$131.37	$131.35	$131.40
Purchase #3	$113.42	9.238%	$123.8977	$123.90	$123.90	$123.90
Purchase #4	$244.43	3.617%	$253.271	$253.27	$253.25	$253.30
Purchase #5	$136.89	3.104%	$141.1391	$141.14	$141.15	$141.10
Purchase #6	$130.35	8.789%	$141.8065	$141.81	$141.80	$141.80
Purchase #7	$10.96	4.727%	$11.4781	$11.48	$11.50	$11.50
7 purchase totals =	$962.18		$1,012.6131	$1,012.62	$1,012.60	$1,012.60