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	$107.94	10.577%	$119.3568	$119.36	$119.35	$119.40
Purchase #2	$87.87	7.503%	$94.4629	$94.46	$94.45	$94.50
Purchase #3	$42.93	13.194%	$48.5942	$48.59	$48.60	$48.60
Purchase #4	$250.69	5.615%	$264.7662	$264.77	$264.75	$264.80
Purchase #5	$233.66	4.301%	$243.7097	$243.71	$243.70	$243.70
Purchase #6	$222.82	9.456%	$243.8899	$243.89	$243.90	$243.90
Purchase #7	$22.94	9.108%	$25.0294	$25.03	$25.05	$25.00
7 purchase totals =	$968.85		$1,039.8091	$1,039.81	$1,039.80	$1,039.90