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	$159.46	8.456%	$172.9439	$172.94	$172.95	$172.90
Purchase #2	$121.27	8.508%	$131.5877	$131.59	$131.60	$131.60
Purchase #3	$41.39	5.721%	$43.7579	$43.76	$43.75	$43.80
Purchase #4	$59.63	5.310%	$62.7964	$62.80	$62.80	$62.80
Purchase #5	$132.55	5.739%	$140.157	$140.16	$140.15	$140.20
Purchase #6	$30.54	8.555%	$33.1527	$33.15	$33.15	$33.20
Purchase #7	$124.73	6.437%	$132.7589	$132.76	$132.75	$132.80
7 purchase totals =	$669.57		$717.1545	$717.16	$717.15	$717.30