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	$166.47	5.372%	$175.4128	$175.41	$175.40	$175.40
Purchase #2	$40.33	8.855%	$43.9012	$43.90	$43.90	$43.90
Purchase #3	$184.72	10.164%	$203.4949	$203.49	$203.50	$203.50
Purchase #4	$153.57	10.442%	$169.6058	$169.61	$169.60	$169.60
Purchase #5	$31.46	4.421%	$32.8508	$32.85	$32.85	$32.90
Purchase #6	$61.81	3.787%	$64.1507	$64.15	$64.15	$64.20
Purchase #7	$250.54	8.552%	$271.9662	$271.97	$271.95	$272.00
7 purchase totals =	$888.90		$961.3824	$961.38	$961.35	$961.50