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	$154.49	11.230%	$171.8392	$171.84	$171.85	$171.80
Purchase #2	$219.88	6.164%	$233.4334	$233.43	$233.45	$233.40
Purchase #3	$129.61	5.291%	$136.4677	$136.47	$136.45	$136.50
Purchase #4	$111.48	7.451%	$119.7864	$119.79	$119.80	$119.80
Purchase #5	$138.54	7.163%	$148.4636	$148.46	$148.45	$148.50
Purchase #6	$69.88	8.722%	$75.9749	$75.97	$75.95	$76.00
Purchase #7	$237.60	11.342%	$264.5486	$264.55	$264.55	$264.50
7 purchase totals =	$1,061.48		$1,150.5138	$1,150.51	$1,150.50	$1,150.50