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	$233.48	3.259%	$241.0891	$241.09	$241.10	$241.10
Purchase #2	$182.25	5.571%	$192.4031	$192.40	$192.40	$192.40
Purchase #3	$39.40	3.672%	$40.8468	$40.85	$40.85	$40.80
Purchase #4	$243.31	3.516%	$251.8648	$251.86	$251.85	$251.90
Purchase #5	$53.36	10.288%	$58.8497	$58.85	$58.85	$58.80
Purchase #6	$37.89	9.406%	$41.4539	$41.45	$41.45	$41.50
Purchase #7	$36.49	4.181%	$38.0156	$38.02	$38.00	$38.00
7 purchase totals =	$826.18		$864.5230	$864.52	$864.50	$864.50