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	$105.50	5.768%	$111.5852	$111.59	$111.60	$111.60
Purchase #2	$21.89	3.567%	$22.6708	$22.67	$22.65	$22.70
Purchase #3	$185.97	13.224%	$210.5627	$210.56	$210.55	$210.60
Purchase #4	$152.31	3.753%	$158.0262	$158.03	$158.05	$158.00
Purchase #5	$239.78	6.724%	$255.9028	$255.90	$255.90	$255.90
Purchase #6	$112.71	9.792%	$123.7466	$123.75	$123.75	$123.70
Purchase #7	$43.61	9.537%	$47.7691	$47.77	$47.75	$47.80
7 purchase totals =	$861.77		$930.2634	$930.27	$930.25	$930.30