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	$79.26	5.198%	$83.3799	$83.38	$83.40	$83.40
Purchase #2	$167.63	5.526%	$176.8932	$176.89	$176.90	$176.90
Purchase #3	$33.28	7.334%	$35.7208	$35.72	$35.70	$35.70
Purchase #4	$136.85	6.757%	$146.097	$146.10	$146.10	$146.10
Purchase #5	$236.39	7.752%	$254.715	$254.72	$254.70	$254.70
Purchase #6	$153.54	5.416%	$161.8557	$161.86	$161.85	$161.90
Purchase #7	$184.82	6.562%	$196.9479	$196.95	$196.95	$196.90
7 purchase totals =	$991.77		$1,055.6095	$1,055.62	$1,055.60	$1,055.60