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	$147.70	12.711%	$166.4741	$166.47	$166.45	$166.50
Purchase #2	$34.73	7.482%	$37.3285	$37.33	$37.35	$37.30
Purchase #3	$102.61	9.170%	$112.0193	$112.02	$112.00	$112.00
Purchase #4	$94.41	11.393%	$105.1661	$105.17	$105.15	$105.20
Purchase #5	$236.47	12.842%	$266.8375	$266.84	$266.85	$266.80
Purchase #6	$31.63	4.189%	$32.955	$32.96	$32.95	$33.00
Purchase #7	$40.65	7.670%	$43.7679	$43.77	$43.75	$43.80
7 purchase totals =	$688.20		$764.5484	$764.56	$764.50	$764.60