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	$97.58	3.263%	$100.764	$100.76	$100.75	$100.80
Purchase #2	$95.27	5.616%	$100.6204	$100.62	$100.60	$100.60
Purchase #3	$155.60	10.828%	$172.4484	$172.45	$172.45	$172.40
Purchase #4	$210.66	3.784%	$218.6314	$218.63	$218.65	$218.60
Purchase #5	$67.54	3.407%	$69.8411	$69.84	$69.85	$69.80
Purchase #6	$152.49	5.293%	$160.5613	$160.56	$160.55	$160.60
Purchase #7	$103.62	8.573%	$112.5033	$112.50	$112.50	$112.50
7 purchase totals =	$882.76		$935.3699	$935.36	$935.35	$935.30