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	$116.32	12.295%	$130.6215	$130.62	$130.60	$130.60
Purchase #2	$239.66	6.223%	$254.574	$254.57	$254.55	$254.60
Purchase #3	$123.54	13.550%	$140.2797	$140.28	$140.30	$140.30
Purchase #4	$200.57	13.573%	$227.7934	$227.79	$227.80	$227.80
Purchase #5	$40.58	7.104%	$43.4628	$43.46	$43.45	$43.50
Purchase #6	$147.90	11.165%	$164.413	$164.41	$164.40	$164.40
Purchase #7	$14.74	6.650%	$15.7202	$15.72	$15.70	$15.70
7 purchase totals =	$883.31		$976.8646	$976.85	$976.80	$976.90