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	$117.55	7.726%	$126.6319	$126.63	$126.65	$126.60
Purchase #2	$213.84	12.363%	$240.277	$240.28	$240.30	$240.30
Purchase #3	$100.37	10.404%	$110.8125	$110.81	$110.80	$110.80
Purchase #4	$37.61	12.314%	$42.2413	$42.24	$42.25	$42.20
Purchase #5	$167.37	12.434%	$188.1808	$188.18	$188.20	$188.20
Purchase #6	$166.73	3.173%	$172.0203	$172.02	$172.00	$172.00
Purchase #7	$50.48	10.284%	$55.6714	$55.67	$55.65	$55.70
7 purchase totals =	$853.95		$935.8352	$935.83	$935.85	$935.80