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	$21.31	4.759%	$22.3241	$22.32	$22.30	$22.30
Purchase #2	$157.89	11.328%	$175.7758	$175.78	$175.80	$175.80
Purchase #3	$148.82	3.800%	$154.4752	$154.48	$154.50	$154.50
Purchase #4	$235.85	8.427%	$255.7251	$255.73	$255.75	$255.70
Purchase #5	$216.66	7.769%	$233.4923	$233.49	$233.50	$233.50
Purchase #6	$215.25	3.477%	$222.7342	$222.73	$222.75	$222.70
Purchase #7	$95.44	4.466%	$99.7024	$99.70	$99.70	$99.70
7 purchase totals =	$1,091.22		$1,164.2291	$1,164.23	$1,164.30	$1,164.20