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	$109.88	6.127%	$116.6123	$116.61	$116.60	$116.60
Purchase #2	$203.75	12.655%	$229.5346	$229.53	$229.55	$229.50
Purchase #3	$219.47	10.443%	$242.3893	$242.39	$242.40	$242.40
Purchase #4	$157.37	5.280%	$165.6791	$165.68	$165.70	$165.70
Purchase #5	$23.31	5.582%	$24.6112	$24.61	$24.60	$24.60
Purchase #6	$210.84	4.413%	$220.1444	$220.14	$220.15	$220.10
Purchase #7	$234.85	9.243%	$256.5572	$256.56	$256.55	$256.60
7 purchase totals =	$1,159.47		$1,255.5281	$1,255.52	$1,255.55	$1,255.50