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	$34.50	3.527%	$35.7168	$35.72	$35.70	$35.70
Purchase #2	$155.89	10.654%	$172.4985	$172.50	$172.50	$172.50
Purchase #3	$194.49	10.705%	$215.3102	$215.31	$215.30	$215.30
Purchase #4	$226.55	7.547%	$243.6477	$243.65	$243.65	$243.60
Purchase #5	$95.25	3.694%	$98.7685	$98.77	$98.75	$98.80
Purchase #6	$72.64	8.863%	$79.0781	$79.08	$79.10	$79.10
Purchase #7	$234.41	8.867%	$255.1951	$255.20	$255.20	$255.20
7 purchase totals =	$1,013.73		$1,100.2149	$1,100.23	$1,100.20	$1,100.20