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	$63.32	5.735%	$66.9514	$66.95	$66.95	$67.00
Purchase #2	$112.90	3.529%	$116.8842	$116.88	$116.90	$116.90
Purchase #3	$18.97	7.870%	$20.4629	$20.46	$20.45	$20.50
Purchase #4	$62.80	10.746%	$69.5485	$69.55	$69.55	$69.50
Purchase #5	$160.96	8.669%	$174.9136	$174.91	$174.90	$174.90
Purchase #6	$143.83	5.286%	$151.4329	$151.43	$151.45	$151.40
Purchase #7	$135.73	3.648%	$140.6814	$140.68	$140.70	$140.70
7 purchase totals =	$698.51		$740.8749	$740.86	$740.90	$740.90