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	$228.30	11.699%	$255.0088	$255.01	$255.00	$255.00
Purchase #2	$64.98	6.620%	$69.2817	$69.28	$69.30	$69.30
Purchase #3	$90.89	7.811%	$97.9894	$97.99	$98.00	$98.00
Purchase #4	$224.80	13.441%	$255.0154	$255.02	$255.00	$255.00
Purchase #5	$106.89	10.872%	$118.5111	$118.51	$118.50	$118.50
Purchase #6	$25.61	13.804%	$29.1452	$29.15	$29.15	$29.10
Purchase #7	$197.73	12.761%	$222.9623	$222.96	$222.95	$223.00
7 purchase totals =	$939.20		$1,047.9139	$1,047.92	$1,047.90	$1,047.90