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	$186.68	12.551%	$210.1102	$210.11	$210.10	$210.10
Purchase #2	$218.51	10.824%	$242.1615	$242.16	$242.15	$242.20
Purchase #3	$177.40	7.195%	$190.1639	$190.16	$190.15	$190.20
Purchase #4	$7.25	6.473%	$7.7193	$7.72	$7.70	$7.70
Purchase #5	$222.40	7.377%	$238.8064	$238.81	$238.80	$238.80
Purchase #6	$41.55	12.520%	$46.7521	$46.75	$46.75	$46.80
Purchase #7	$247.36	5.518%	$261.0093	$261.01	$261.00	$261.00
7 purchase totals =	$1,101.15		$1,196.7227	$1,196.72	$1,196.65	$1,196.80