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	$70.82	8.129%	$76.577	$76.58	$76.60	$76.60
Purchase #2	$149.62	7.271%	$160.4989	$160.50	$160.50	$160.50
Purchase #3	$32.96	7.807%	$35.5332	$35.53	$35.55	$35.50
Purchase #4	$210.79	5.199%	$221.749	$221.75	$221.75	$221.70
Purchase #5	$65.28	3.238%	$67.3938	$67.39	$67.40	$67.40
Purchase #6	$136.60	12.410%	$153.5521	$153.55	$153.55	$153.60
Purchase #7	$59.32	12.259%	$66.592	$66.59	$66.60	$66.60
7 purchase totals =	$725.39		$781.8960	$781.89	$781.95	$781.90