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	$34.28	8.246%	$37.1067	$37.11	$37.10	$37.10
Purchase #2	$101.36	6.377%	$107.8237	$107.82	$107.80	$107.80
Purchase #3	$227.90	3.170%	$235.1244	$235.12	$235.10	$235.10
Purchase #4	$218.34	3.268%	$225.4754	$225.48	$225.50	$225.50
Purchase #5	$145.48	4.661%	$152.2608	$152.26	$152.25	$152.30
Purchase #6	$78.53	9.328%	$85.8553	$85.86	$85.85	$85.90
Purchase #7	$63.57	12.562%	$71.5557	$71.56	$71.55	$71.60
7 purchase totals =	$869.46		$915.2020	$915.21	$915.15	$915.30