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	$180.98	4.207%	$188.5938	$188.59	$188.60	$188.60
Purchase #2	$13.44	7.737%	$14.4799	$14.48	$14.50	$14.50
Purchase #3	$72.67	11.644%	$81.1317	$81.13	$81.15	$81.10
Purchase #4	$99.81	9.303%	$109.0953	$109.10	$109.10	$109.10
Purchase #5	$46.37	11.499%	$51.7021	$51.70	$51.70	$51.70
Purchase #6	$58.82	10.316%	$64.8879	$64.89	$64.90	$64.90
Purchase #7	$119.60	12.518%	$134.5715	$134.57	$134.55	$134.60
7 purchase totals =	$591.69		$644.4622	$644.46	$644.50	$644.50