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	$198.46	8.576%	$215.4799	$215.48	$215.50	$215.50
Purchase #2	$95.33	5.205%	$100.2919	$100.29	$100.30	$100.30
Purchase #3	$188.33	9.709%	$206.615	$206.62	$206.60	$206.60
Purchase #4	$44.64	12.658%	$50.2905	$50.29	$50.30	$50.30
Purchase #5	$31.93	10.863%	$35.3986	$35.40	$35.40	$35.40
Purchase #6	$245.93	3.781%	$255.2286	$255.23	$255.25	$255.20
Purchase #7	$203.52	7.592%	$218.9712	$218.97	$218.95	$219.00
7 purchase totals =	$1,008.14		$1,082.2757	$1,082.28	$1,082.30	$1,082.30