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	$214.60	4.606%	$224.4845	$224.48	$224.50	$224.50
Purchase #2	$53.33	3.766%	$55.3384	$55.34	$55.35	$55.30
Purchase #3	$156.61	6.540%	$166.8523	$166.85	$166.85	$166.90
Purchase #4	$165.65	5.317%	$174.4576	$174.46	$174.45	$174.50
Purchase #5	$250.93	6.855%	$268.1313	$268.13	$268.15	$268.10
Purchase #6	$216.77	13.540%	$246.1207	$246.12	$246.10	$246.10
Purchase #7	$43.73	3.576%	$45.2938	$45.29	$45.30	$45.30
7 purchase totals =	$1,101.62		$1,180.6786	$1,180.67	$1,180.70	$1,180.70