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	$198.99	7.265%	$213.4466	$213.45	$213.45	$213.40
Purchase #2	$62.67	6.691%	$66.8632	$66.86	$66.85	$66.90
Purchase #3	$55.67	11.103%	$61.851	$61.85	$61.85	$61.90
Purchase #4	$108.32	3.289%	$111.8826	$111.88	$111.90	$111.90
Purchase #5	$136.50	5.473%	$143.9706	$143.97	$143.95	$144.00
Purchase #6	$81.34	6.824%	$86.8906	$86.89	$86.90	$86.90
Purchase #7	$5.69	12.596%	$6.4067	$6.41	$6.40	$6.40
7 purchase totals =	$649.18		$691.3113	$691.31	$691.30	$691.40