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	$230.39	7.445%	$247.5425	$247.54	$247.55	$247.50
Purchase #2	$44.62	12.189%	$50.0587	$50.06	$50.05	$50.10
Purchase #3	$40.48	8.712%	$44.0066	$44.01	$44.00	$44.00
Purchase #4	$37.49	8.234%	$40.5769	$40.58	$40.60	$40.60
Purchase #5	$29.71	4.362%	$31.006	$31.01	$31.00	$31.00
Purchase #6	$243.71	4.858%	$255.5494	$255.55	$255.55	$255.50
Purchase #7	$143.78	8.820%	$156.4614	$156.46	$156.45	$156.50
7 purchase totals =	$770.18		$825.2015	$825.21	$825.20	$825.20