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	$183.42	10.199%	$202.127	$202.13	$202.15	$202.10
Purchase #2	$80.50	3.708%	$83.4849	$83.48	$83.50	$83.50
Purchase #3	$24.72	5.626%	$26.1107	$26.11	$26.10	$26.10
Purchase #4	$93.42	11.441%	$104.1082	$104.11	$104.10	$104.10
Purchase #5	$114.26	4.570%	$119.4817	$119.48	$119.50	$119.50
Purchase #6	$141.38	7.105%	$151.425	$151.43	$151.45	$151.40
Purchase #7	$241.65	5.638%	$255.2742	$255.27	$255.25	$255.30
7 purchase totals =	$879.35		$942.0117	$942.01	$942.05	$942.00