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	$221.36	9.724%	$242.885	$242.89	$242.90	$242.90
Purchase #2	$48.89	7.150%	$52.3856	$52.39	$52.40	$52.40
Purchase #3	$25.33	10.446%	$27.976	$27.98	$28.00	$28.00
Purchase #4	$203.50	5.546%	$214.7861	$214.79	$214.80	$214.80
Purchase #5	$57.51	12.824%	$64.8851	$64.89	$64.90	$64.90
Purchase #6	$250.44	7.785%	$269.9368	$269.94	$269.95	$269.90
Purchase #7	$250.97	11.132%	$278.908	$278.91	$278.90	$278.90
7 purchase totals =	$1,058.00		$1,151.7626	$1,151.79	$1,151.85	$1,151.80