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	$192.97	13.539%	$219.0962	$219.10	$219.10	$219.10
Purchase #2	$123.86	10.388%	$136.7266	$136.73	$136.75	$136.70
Purchase #3	$48.79	12.485%	$54.8814	$54.88	$54.90	$54.90
Purchase #4	$248.79	10.857%	$275.8011	$275.80	$275.80	$275.80
Purchase #5	$19.82	3.392%	$20.4923	$20.49	$20.50	$20.50
Purchase #6	$193.61	3.201%	$199.8075	$199.81	$199.80	$199.80
Purchase #7	$247.96	3.288%	$256.1129	$256.11	$256.10	$256.10
7 purchase totals =	$1,075.80		$1,162.9180	$1,162.92	$1,162.95	$1,162.90