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	$147.76	8.385%	$160.1497	$160.15	$160.15	$160.10
Purchase #2	$34.73	3.244%	$35.8566	$35.86	$35.85	$35.90
Purchase #3	$230.64	11.296%	$256.6931	$256.69	$256.70	$256.70
Purchase #4	$96.66	7.517%	$103.9259	$103.93	$103.95	$103.90
Purchase #5	$79.70	9.280%	$87.0962	$87.10	$87.10	$87.10
Purchase #6	$96.62	13.406%	$109.5729	$109.57	$109.55	$109.60
Purchase #7	$30.77	5.873%	$32.5771	$32.58	$32.60	$32.60
7 purchase totals =	$716.88		$785.8715	$785.88	$785.90	$785.90