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	$213.57	6.767%	$228.0223	$228.02	$228.00	$228.00
Purchase #2	$247.64	3.662%	$256.7086	$256.71	$256.70	$256.70
Purchase #3	$9.62	12.871%	$10.8582	$10.86	$10.85	$10.90
Purchase #4	$147.30	3.697%	$152.7457	$152.75	$152.75	$152.70
Purchase #5	$189.40	3.754%	$196.5101	$196.51	$196.50	$196.50
Purchase #6	$220.34	9.554%	$241.3913	$241.39	$241.40	$241.40
Purchase #7	$136.27	3.596%	$141.1703	$141.17	$141.15	$141.20
7 purchase totals =	$1,164.14		$1,227.4065	$1,227.41	$1,227.35	$1,227.40