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	$55.85	7.151%	$59.8438	$59.84	$59.85	$59.80
Purchase #2	$43.49	3.678%	$45.0896	$45.09	$45.10	$45.10
Purchase #3	$43.77	3.862%	$45.4604	$45.46	$45.45	$45.50
Purchase #4	$44.40	5.682%	$46.9228	$46.92	$46.90	$46.90
Purchase #5	$93.37	3.332%	$96.4811	$96.48	$96.50	$96.50
Purchase #6	$52.76	11.468%	$58.8105	$58.81	$58.80	$58.80
Purchase #7	$125.75	10.873%	$139.4228	$139.42	$139.40	$139.40
7 purchase totals =	$459.39		$492.0310	$492.02	$492.00	$492.00