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	$116.60	9.794%	$128.0198	$128.02	$128.00	$128.00
Purchase #2	$53.89	10.320%	$59.4514	$59.45	$59.45	$59.50
Purchase #3	$86.81	5.238%	$91.3571	$91.36	$91.35	$91.40
Purchase #4	$241.30	6.626%	$257.2885	$257.29	$257.30	$257.30
Purchase #5	$54.78	6.674%	$58.436	$58.44	$58.45	$58.40
Purchase #6	$29.35	7.304%	$31.4937	$31.49	$31.50	$31.50
Purchase #7	$122.44	9.860%	$134.5126	$134.51	$134.50	$134.50
7 purchase totals =	$705.17		$760.5591	$760.56	$760.55	$760.60