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	$184.55	6.470%	$196.4904	$196.49	$196.50	$196.50
Purchase #2	$241.62	6.145%	$256.4675	$256.47	$256.45	$256.50
Purchase #3	$118.57	13.807%	$134.941	$134.94	$134.95	$134.90
Purchase #4	$212.81	5.313%	$224.1166	$224.12	$224.10	$224.10
Purchase #5	$88.54	10.735%	$98.0448	$98.04	$98.05	$98.00
Purchase #6	$14.37	10.841%	$15.9279	$15.93	$15.95	$15.90
Purchase #7	$43.25	5.331%	$45.5557	$45.56	$45.55	$45.60
7 purchase totals =	$903.71		$971.5439	$971.55	$971.55	$971.50