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	$200.65	7.763%	$216.2265	$216.23	$216.25	$216.20
Purchase #2	$240.62	4.269%	$250.8921	$250.89	$250.90	$250.90
Purchase #3	$213.54	13.404%	$242.1629	$242.16	$242.15	$242.20
Purchase #4	$233.85	13.226%	$264.779	$264.78	$264.80	$264.80
Purchase #5	$61.47	9.782%	$67.483	$67.48	$67.50	$67.50
Purchase #6	$38.30	7.147%	$41.0373	$41.04	$41.05	$41.00
Purchase #7	$152.35	13.266%	$172.5608	$172.56	$172.55	$172.60
7 purchase totals =	$1,140.78		$1,255.1416	$1,255.14	$1,255.20	$1,255.20