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	$73.46	6.324%	$78.1056	$78.11	$78.10	$78.10
Purchase #2	$71.66	9.568%	$78.5164	$78.52	$78.50	$78.50
Purchase #3	$69.96	9.344%	$76.4971	$76.50	$76.50	$76.50
Purchase #4	$239.94	9.186%	$261.9809	$261.98	$262.00	$262.00
Purchase #5	$191.68	9.159%	$209.236	$209.24	$209.25	$209.20
Purchase #6	$182.41	4.107%	$189.9016	$189.90	$189.90	$189.90
Purchase #7	$236.59	8.544%	$256.8042	$256.80	$256.80	$256.80
7 purchase totals =	$1,065.70		$1,151.0418	$1,151.05	$1,151.05	$1,151.00