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	$108.31	6.378%	$115.218	$115.22	$115.20	$115.20
Purchase #2	$142.46	13.397%	$161.5454	$161.55	$161.55	$161.50
Purchase #3	$203.81	9.377%	$222.9213	$222.92	$222.90	$222.90
Purchase #4	$150.33	7.850%	$162.1309	$162.13	$162.15	$162.10
Purchase #5	$104.66	4.619%	$109.4942	$109.49	$109.50	$109.50
Purchase #6	$230.73	3.112%	$237.9103	$237.91	$237.90	$237.90
Purchase #7	$174.98	12.243%	$196.4028	$196.40	$196.40	$196.40
7 purchase totals =	$1,115.28		$1,205.6229	$1,205.62	$1,205.60	$1,205.50