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	$194.33	6.159%	$206.2988	$206.30	$206.30	$206.30
Purchase #2	$241.43	9.313%	$263.9144	$263.91	$263.90	$263.90
Purchase #3	$131.35	6.179%	$139.4661	$139.47	$139.45	$139.50
Purchase #4	$185.31	5.208%	$194.9609	$194.96	$194.95	$195.00
Purchase #5	$36.40	11.412%	$40.554	$40.55	$40.55	$40.60
Purchase #6	$164.26	4.863%	$172.248	$172.25	$172.25	$172.20
Purchase #7	$141.98	9.775%	$155.8585	$155.86	$155.85	$155.90
7 purchase totals =	$1,095.06		$1,173.3007	$1,173.30	$1,173.25	$1,173.40