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	$145.41	5.137%	$152.8797	$152.88	$152.90	$152.90
Purchase #2	$192.71	13.297%	$218.3346	$218.33	$218.35	$218.30
Purchase #3	$83.90	12.632%	$94.4982	$94.50	$94.50	$94.50
Purchase #4	$244.60	8.460%	$265.2932	$265.29	$265.30	$265.30
Purchase #5	$138.53	7.486%	$148.9004	$148.90	$148.90	$148.90
Purchase #6	$196.61	13.310%	$222.7788	$222.78	$222.80	$222.80
Purchase #7	$203.56	13.421%	$230.8798	$230.88	$230.90	$230.90
7 purchase totals =	$1,205.32		$1,333.5647	$1,333.56	$1,333.65	$1,333.60