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	$106.63	4.146%	$111.0509	$111.05	$111.05	$111.10
Purchase #2	$117.44	11.805%	$131.3038	$131.30	$131.30	$131.30
Purchase #3	$67.96	12.716%	$76.6018	$76.60	$76.60	$76.60
Purchase #4	$23.45	6.154%	$24.8931	$24.89	$24.90	$24.90
Purchase #5	$200.44	11.133%	$222.755	$222.76	$222.75	$222.80
Purchase #6	$220.61	11.204%	$245.3271	$245.33	$245.35	$245.30
Purchase #7	$92.72	13.797%	$105.5126	$105.51	$105.50	$105.50
7 purchase totals =	$829.25		$917.4443	$917.44	$917.45	$917.50