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	$32.97	8.382%	$35.7335	$35.73	$35.75	$35.70
Purchase #2	$144.44	5.529%	$152.4261	$152.43	$152.45	$152.40
Purchase #3	$185.50	6.124%	$196.86	$196.86	$196.85	$196.90
Purchase #4	$244.34	11.642%	$272.7861	$272.79	$272.80	$272.80
Purchase #5	$214.86	10.759%	$237.9768	$237.98	$238.00	$238.00
Purchase #6	$69.92	11.572%	$78.0111	$78.01	$78.00	$78.00
Purchase #7	$60.92	6.468%	$64.8603	$64.86	$64.85	$64.90
7 purchase totals =	$952.95		$1,038.6539	$1,038.66	$1,038.70	$1,038.70