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	$94.59	5.309%	$99.6118	$99.61	$99.60	$99.60
Purchase #2	$105.59	10.315%	$116.4816	$116.48	$116.50	$116.50
Purchase #3	$244.56	3.591%	$253.3421	$253.34	$253.35	$253.30
Purchase #4	$72.71	12.240%	$81.6097	$81.61	$81.60	$81.60
Purchase #5	$11.49	8.262%	$12.4393	$12.44	$12.45	$12.40
Purchase #6	$91.90	6.259%	$97.652	$97.65	$97.65	$97.70
Purchase #7	$80.52	3.389%	$83.2488	$83.25	$83.25	$83.20
7 purchase totals =	$701.36		$744.3853	$744.38	$744.40	$744.30