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	$172.41	4.662%	$180.4478	$180.45	$180.45	$180.40
Purchase #2	$104.47	10.241%	$115.1688	$115.17	$115.15	$115.20
Purchase #3	$198.57	3.505%	$205.5299	$205.53	$205.55	$205.50
Purchase #4	$87.96	3.215%	$90.7879	$90.79	$90.80	$90.80
Purchase #5	$167.29	9.310%	$182.8647	$182.86	$182.85	$182.90
Purchase #6	$51.43	7.644%	$55.3613	$55.36	$55.35	$55.40
Purchase #7	$151.63	13.793%	$172.5443	$172.54	$172.55	$172.50
7 purchase totals =	$933.76		$1,002.7047	$1,002.70	$1,002.70	$1,002.70