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	$92.82	10.835%	$102.877	$102.88	$102.90	$102.90
Purchase #2	$134.81	13.377%	$152.8435	$152.84	$152.85	$152.80
Purchase #3	$243.46	13.294%	$275.8256	$275.83	$275.85	$275.80
Purchase #4	$59.45	12.357%	$66.7962	$66.80	$66.80	$66.80
Purchase #5	$65.59	3.231%	$67.7092	$67.71	$67.70	$67.70
Purchase #6	$102.38	9.272%	$111.8727	$111.87	$111.85	$111.90
Purchase #7	$7.96	11.422%	$8.8692	$8.87	$8.85	$8.90
7 purchase totals =	$706.47		$786.7934	$786.80	$786.80	$786.80