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	$21.33	5.151%	$22.4287	$22.43	$22.45	$22.40
Purchase #2	$84.42	13.634%	$95.9298	$95.93	$95.95	$95.90
Purchase #3	$26.50	5.114%	$27.8552	$27.86	$27.85	$27.90
Purchase #4	$177.28	12.873%	$200.1013	$200.10	$200.10	$200.10
Purchase #5	$17.82	3.380%	$18.4223	$18.42	$18.40	$18.40
Purchase #6	$35.83	13.284%	$40.5897	$40.59	$40.60	$40.60
Purchase #7	$143.41	13.242%	$162.4004	$162.40	$162.40	$162.40
7 purchase totals =	$506.59		$567.7274	$567.73	$567.75	$567.70