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	$226.40	5.501%	$238.8543	$238.85	$238.85	$238.90
Purchase #2	$212.94	4.363%	$222.2306	$222.23	$222.25	$222.20
Purchase #3	$85.69	6.152%	$90.9616	$90.96	$90.95	$91.00
Purchase #4	$38.38	10.605%	$42.4502	$42.45	$42.45	$42.50
Purchase #5	$47.63	13.194%	$53.9143	$53.91	$53.90	$53.90
Purchase #6	$81.35	6.451%	$86.5979	$86.60	$86.60	$86.60
Purchase #7	$170.61	10.394%	$188.3432	$188.34	$188.35	$188.30
7 purchase totals =	$863.00		$923.3521	$923.34	$923.35	$923.40