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	$66.43	7.768%	$71.5903	$71.59	$71.60	$71.60
Purchase #2	$201.60	3.185%	$208.021	$208.02	$208.00	$208.00
Purchase #3	$230.88	5.309%	$243.1374	$243.14	$243.15	$243.10
Purchase #4	$241.85	5.711%	$255.6621	$255.66	$255.65	$255.70
Purchase #5	$142.51	5.507%	$150.358	$150.36	$150.35	$150.40
Purchase #6	$78.77	12.806%	$88.8573	$88.86	$88.85	$88.90
Purchase #7	$185.42	3.497%	$191.9041	$191.90	$191.90	$191.90
7 purchase totals =	$1,147.46		$1,209.5302	$1,209.53	$1,209.50	$1,209.60