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	$85.96	8.611%	$93.362	$93.36	$93.35	$93.40
Purchase #2	$130.70	12.419%	$146.9316	$146.93	$146.95	$146.90
Purchase #3	$76.42	12.743%	$86.1582	$86.16	$86.15	$86.20
Purchase #4	$84.81	13.372%	$96.1508	$96.15	$96.15	$96.20
Purchase #5	$7.45	5.705%	$7.875	$7.88	$7.90	$7.90
Purchase #6	$70.94	10.633%	$78.4831	$78.48	$78.50	$78.50
Purchase #7	$184.92	13.269%	$209.457	$209.46	$209.45	$209.50
7 purchase totals =	$641.20		$718.4177	$718.42	$718.45	$718.60