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	$225.33	5.704%	$238.1828	$238.18	$238.20	$238.20
Purchase #2	$186.89	11.563%	$208.5001	$208.50	$208.50	$208.50
Purchase #3	$81.66	12.171%	$91.5988	$91.60	$91.60	$91.60
Purchase #4	$52.51	4.159%	$54.6939	$54.69	$54.70	$54.70
Purchase #5	$105.67	11.557%	$117.8823	$117.88	$117.90	$117.90
Purchase #6	$125.32	8.215%	$135.615	$135.62	$135.60	$135.60
Purchase #7	$233.95	8.741%	$254.3996	$254.40	$254.40	$254.40
7 purchase totals =	$1,011.33		$1,100.8725	$1,100.87	$1,100.90	$1,100.90