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	$140.33	7.521%	$150.8842	$150.88	$150.90	$150.90
Purchase #2	$62.98	13.378%	$71.4055	$71.41	$71.40	$71.40
Purchase #3	$132.57	7.314%	$142.2662	$142.27	$142.25	$142.30
Purchase #4	$207.73	9.797%	$228.0813	$228.08	$228.10	$228.10
Purchase #5	$225.49	13.448%	$255.8139	$255.81	$255.80	$255.80
Purchase #6	$40.76	11.418%	$45.414	$45.41	$45.40	$45.40
Purchase #7	$242.83	8.431%	$263.303	$263.30	$263.30	$263.30
7 purchase totals =	$1,052.69		$1,157.1681	$1,157.16	$1,157.15	$1,157.20