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	$249.29	5.301%	$262.5049	$262.50	$262.50	$262.50
Purchase #2	$132.69	7.146%	$142.172	$142.17	$142.15	$142.20
Purchase #3	$87.41	5.445%	$92.1695	$92.17	$92.15	$92.20
Purchase #4	$161.57	3.855%	$167.7985	$167.80	$167.80	$167.80
Purchase #5	$53.96	10.497%	$59.6242	$59.62	$59.60	$59.60
Purchase #6	$228.46	6.586%	$243.5064	$243.51	$243.50	$243.50
Purchase #7	$222.47	4.856%	$233.2731	$233.27	$233.25	$233.30
7 purchase totals =	$1,135.85		$1,201.0486	$1,201.04	$1,200.95	$1,201.10