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	$153.67	12.230%	$172.4638	$172.46	$172.45	$172.50
Purchase #2	$30.86	10.730%	$34.1713	$34.17	$34.15	$34.20
Purchase #3	$224.35	12.315%	$251.9787	$251.98	$252.00	$252.00
Purchase #4	$241.75	6.782%	$258.1455	$258.15	$258.15	$258.10
Purchase #5	$43.59	3.599%	$45.1588	$45.16	$45.15	$45.20
Purchase #6	$191.97	3.419%	$198.5335	$198.53	$198.55	$198.50
Purchase #7	$210.61	6.777%	$224.883	$224.88	$224.90	$224.90
7 purchase totals =	$1,096.80		$1,185.3346	$1,185.33	$1,185.35	$1,185.40