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	$104.91	13.564%	$119.14	$119.14	$119.15	$119.10
Purchase #2	$152.66	9.607%	$167.326	$167.33	$167.35	$167.30
Purchase #3	$37.47	7.663%	$40.3413	$40.34	$40.35	$40.30
Purchase #4	$140.59	4.831%	$147.3819	$147.38	$147.40	$147.40
Purchase #5	$113.94	11.331%	$126.8505	$126.85	$126.85	$126.90
Purchase #6	$92.71	11.160%	$103.0564	$103.06	$103.05	$103.10
Purchase #7	$241.67	12.259%	$271.2963	$271.30	$271.30	$271.30
7 purchase totals =	$883.95		$975.3924	$975.40	$975.45	$975.40