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	$28.58	9.692%	$31.35	$31.35	$31.35	$31.40
Purchase #2	$239.38	5.606%	$252.7996	$252.80	$252.80	$252.80
Purchase #3	$24.61	12.717%	$27.7397	$27.74	$27.75	$27.70
Purchase #4	$99.91	8.692%	$108.5942	$108.59	$108.60	$108.60
Purchase #5	$82.76	3.302%	$85.4927	$85.49	$85.50	$85.50
Purchase #6	$192.33	4.127%	$200.2675	$200.27	$200.25	$200.30
Purchase #7	$32.96	7.129%	$35.3097	$35.31	$35.30	$35.30
7 purchase totals =	$700.53		$741.5534	$741.55	$741.55	$741.60