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	$183.92	8.427%	$199.4189	$199.42	$199.40	$199.40
Purchase #2	$30.37	3.693%	$31.4916	$31.49	$31.50	$31.50
Purchase #3	$193.62	9.219%	$211.4698	$211.47	$211.45	$211.50
Purchase #4	$17.71	10.349%	$19.5428	$19.54	$19.55	$19.50
Purchase #5	$111.83	11.249%	$124.4098	$124.41	$124.40	$124.40
Purchase #6	$154.42	9.697%	$169.3941	$169.39	$169.40	$169.40
Purchase #7	$73.47	6.736%	$78.4189	$78.42	$78.40	$78.40
7 purchase totals =	$765.34		$834.1459	$834.14	$834.10	$834.10