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	$219.72	13.398%	$249.1581	$249.16	$249.15	$249.20
Purchase #2	$246.27	5.594%	$260.0463	$260.05	$260.05	$260.00
Purchase #3	$141.65	5.197%	$149.0116	$149.01	$149.00	$149.00
Purchase #4	$155.36	10.404%	$171.5237	$171.52	$171.50	$171.50
Purchase #5	$151.43	4.782%	$158.6714	$158.67	$158.65	$158.70
Purchase #6	$188.40	4.517%	$196.91	$196.91	$196.90	$196.90
Purchase #7	$131.39	7.519%	$141.2692	$141.27	$141.25	$141.30
7 purchase totals =	$1,234.22		$1,326.5903	$1,326.59	$1,326.50	$1,326.60