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	$40.78	12.447%	$45.8559	$45.86	$45.85	$45.90
Purchase #2	$58.90	3.747%	$61.107	$61.11	$61.10	$61.10
Purchase #3	$112.81	12.157%	$126.5243	$126.52	$126.50	$126.50
Purchase #4	$75.95	3.825%	$78.8551	$78.86	$78.85	$78.90
Purchase #5	$32.66	8.558%	$35.455	$35.46	$35.45	$35.50
Purchase #6	$115.70	11.234%	$128.6977	$128.70	$128.70	$128.70
Purchase #7	$207.49	12.201%	$232.8059	$232.81	$232.80	$232.80
7 purchase totals =	$644.29		$709.3009	$709.32	$709.25	$709.40