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	$85.70	9.203%	$93.587	$93.59	$93.60	$93.60
Purchase #2	$27.72	8.284%	$30.0163	$30.02	$30.00	$30.00
Purchase #3	$109.58	12.551%	$123.3334	$123.33	$123.35	$123.30
Purchase #4	$211.46	6.460%	$225.1203	$225.12	$225.10	$225.10
Purchase #5	$73.56	7.240%	$78.8857	$78.89	$78.90	$78.90
Purchase #6	$185.36	12.714%	$208.9267	$208.93	$208.95	$208.90
Purchase #7	$243.33	12.136%	$272.8605	$272.86	$272.85	$272.90
7 purchase totals =	$936.71		$1,032.7299	$1,032.74	$1,032.75	$1,032.70