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	$248.35	3.452%	$256.923	$256.92	$256.90	$256.90
Purchase #2	$183.59	3.439%	$189.9037	$189.90	$189.90	$189.90
Purchase #3	$125.82	11.272%	$140.0024	$140.00	$140.00	$140.00
Purchase #4	$107.35	5.751%	$113.5237	$113.52	$113.50	$113.50
Purchase #5	$147.83	3.220%	$152.5901	$152.59	$152.60	$152.60
Purchase #6	$201.28	13.766%	$228.9882	$228.99	$229.00	$229.00
Purchase #7	$84.84	6.668%	$90.4971	$90.50	$90.50	$90.50
7 purchase totals =	$1,099.06		$1,172.4282	$1,172.42	$1,172.40	$1,172.40