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	$66.33	7.744%	$71.4666	$71.47	$71.45	$71.50
Purchase #2	$90.93	7.805%	$98.0271	$98.03	$98.05	$98.00
Purchase #3	$81.37	5.498%	$85.8437	$85.84	$85.85	$85.80
Purchase #4	$214.58	10.871%	$237.907	$237.91	$237.90	$237.90
Purchase #5	$192.94	9.584%	$211.4314	$211.43	$211.45	$211.40
Purchase #6	$75.80	9.861%	$83.2746	$83.27	$83.25	$83.30
Purchase #7	$187.30	11.254%	$208.3787	$208.38	$208.40	$208.40
7 purchase totals =	$909.25		$996.3291	$996.33	$996.35	$996.30