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	$62.76	13.710%	$71.3644	$71.36	$71.35	$71.40
Purchase #2	$66.29	10.729%	$73.4023	$73.40	$73.40	$73.40
Purchase #3	$179.80	8.514%	$195.1082	$195.11	$195.10	$195.10
Purchase #4	$118.70	9.478%	$129.9504	$129.95	$129.95	$130.00
Purchase #5	$68.70	4.249%	$71.6191	$71.62	$71.60	$71.60
Purchase #6	$40.84	4.279%	$42.5875	$42.59	$42.60	$42.60
Purchase #7	$73.40	6.482%	$78.1578	$78.16	$78.15	$78.20
7 purchase totals =	$610.49		$662.1897	$662.19	$662.15	$662.30