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	$138.86	10.839%	$153.911	$153.91	$153.90	$153.90
Purchase #2	$102.98	10.394%	$113.6837	$113.68	$113.70	$113.70
Purchase #3	$101.93	4.227%	$106.2386	$106.24	$106.25	$106.20
Purchase #4	$122.58	6.759%	$130.8652	$130.87	$130.85	$130.90
Purchase #5	$127.57	3.389%	$131.8933	$131.89	$131.90	$131.90
Purchase #6	$190.83	11.867%	$213.4758	$213.48	$213.50	$213.50
Purchase #7	$216.33	13.150%	$244.7774	$244.78	$244.80	$244.80
7 purchase totals =	$1,001.08		$1,094.8450	$1,094.85	$1,094.90	$1,094.90