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	$47.47	7.164%	$50.8708	$50.87	$50.85	$50.90
Purchase #2	$129.47	7.538%	$139.2294	$139.23	$139.25	$139.20
Purchase #3	$67.40	6.675%	$71.899	$71.90	$71.90	$71.90
Purchase #4	$35.56	3.466%	$36.7925	$36.79	$36.80	$36.80
Purchase #5	$155.32	7.739%	$167.3402	$167.34	$167.35	$167.30
Purchase #6	$18.97	8.330%	$20.5502	$20.55	$20.55	$20.60
Purchase #7	$207.54	7.299%	$222.6883	$222.69	$222.70	$222.70
7 purchase totals =	$661.73		$709.3704	$709.37	$709.40	$709.40