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	$244.41	9.574%	$267.8098	$267.81	$267.80	$267.80
Purchase #2	$83.83	8.381%	$90.8558	$90.86	$90.85	$90.90
Purchase #3	$57.56	7.115%	$61.6554	$61.66	$61.65	$61.70
Purchase #4	$232.28	3.410%	$240.2007	$240.20	$240.20	$240.20
Purchase #5	$196.84	8.365%	$213.3057	$213.31	$213.30	$213.30
Purchase #6	$18.72	8.655%	$20.3402	$20.34	$20.35	$20.30
Purchase #7	$142.30	7.657%	$153.1959	$153.20	$153.20	$153.20
7 purchase totals =	$975.94		$1,047.3635	$1,047.38	$1,047.35	$1,047.40