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	$159.93	13.732%	$181.8916	$181.89	$181.90	$181.90
Purchase #2	$209.54	9.440%	$229.3206	$229.32	$229.30	$229.30
Purchase #3	$217.52	9.853%	$238.9522	$238.95	$238.95	$239.00
Purchase #4	$74.75	4.861%	$78.3836	$78.38	$78.40	$78.40
Purchase #5	$6.98	10.451%	$7.7095	$7.71	$7.70	$7.70
Purchase #6	$207.54	7.391%	$222.8793	$222.88	$222.90	$222.90
Purchase #7	$187.77	13.486%	$213.0927	$213.09	$213.10	$213.10
7 purchase totals =	$1,064.03		$1,172.2295	$1,172.22	$1,172.25	$1,172.30