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	$231.81	4.150%	$241.4301	$241.43	$241.45	$241.40
Purchase #2	$20.40	3.606%	$21.1356	$21.14	$21.15	$21.10
Purchase #3	$79.49	3.306%	$82.1179	$82.12	$82.10	$82.10
Purchase #4	$158.59	7.473%	$170.4414	$170.44	$170.45	$170.40
Purchase #5	$123.34	10.776%	$136.6311	$136.63	$136.65	$136.60
Purchase #6	$48.75	10.590%	$53.9126	$53.91	$53.90	$53.90
Purchase #7	$39.91	8.279%	$43.2141	$43.21	$43.20	$43.20
7 purchase totals =	$702.29		$748.8828	$748.88	$748.90	$748.70