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	$37.31	12.118%	$41.8312	$41.83	$41.85	$41.80
Purchase #2	$11.56	11.721%	$12.9149	$12.91	$12.90	$12.90
Purchase #3	$168.94	3.665%	$175.1317	$175.13	$175.15	$175.10
Purchase #4	$38.83	10.577%	$42.937	$42.94	$42.95	$42.90
Purchase #5	$119.26	3.309%	$123.2063	$123.21	$123.20	$123.20
Purchase #6	$232.41	3.580%	$240.7303	$240.73	$240.75	$240.70
Purchase #7	$130.37	11.417%	$145.2543	$145.25	$145.25	$145.30
7 purchase totals =	$738.68		$782.0057	$782.00	$782.05	$781.90