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	$202.39	9.867%	$222.3598	$222.36	$222.35	$222.40
Purchase #2	$34.96	12.220%	$39.2321	$39.23	$39.25	$39.20
Purchase #3	$100.75	4.860%	$105.6465	$105.65	$105.65	$105.60
Purchase #4	$248.27	10.532%	$274.4178	$274.42	$274.40	$274.40
Purchase #5	$86.64	4.667%	$90.6835	$90.68	$90.70	$90.70
Purchase #6	$147.72	8.137%	$159.74	$159.74	$159.75	$159.70
Purchase #7	$150.31	10.187%	$165.6221	$165.62	$165.60	$165.60
7 purchase totals =	$971.04		$1,057.7018	$1,057.70	$1,057.70	$1,057.60