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	$243.48	9.391%	$266.3452	$266.35	$266.35	$266.30
Purchase #2	$66.76	5.685%	$70.5553	$70.56	$70.55	$70.60
Purchase #3	$24.26	13.670%	$27.5763	$27.58	$27.60	$27.60
Purchase #4	$90.57	10.311%	$99.9087	$99.91	$99.90	$99.90
Purchase #5	$144.94	8.740%	$157.6078	$157.61	$157.60	$157.60
Purchase #6	$165.77	7.625%	$178.41	$178.41	$178.40	$178.40
Purchase #7	$211.72	9.221%	$231.2427	$231.24	$231.25	$231.20
7 purchase totals =	$947.50		$1,031.6460	$1,031.66	$1,031.65	$1,031.60