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	$36.63	4.769%	$38.3769	$38.38	$38.40	$38.40
Purchase #2	$143.56	10.498%	$158.6309	$158.63	$158.65	$158.60
Purchase #3	$152.27	5.756%	$161.0347	$161.03	$161.05	$161.00
Purchase #4	$70.91	10.342%	$78.2435	$78.24	$78.25	$78.20
Purchase #5	$189.78	11.386%	$211.3884	$211.39	$211.40	$211.40
Purchase #6	$236.42	11.226%	$262.9605	$262.96	$262.95	$263.00
Purchase #7	$212.49	4.480%	$222.0096	$222.01	$222.00	$222.00
7 purchase totals =	$1,042.06		$1,132.6445	$1,132.64	$1,132.70	$1,132.60