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	$68.50	6.440%	$72.9114	$72.91	$72.90	$72.90
Purchase #2	$125.37	6.811%	$133.909	$133.91	$133.90	$133.90
Purchase #3	$29.81	11.279%	$33.1723	$33.17	$33.15	$33.20
Purchase #4	$57.39	7.699%	$61.8085	$61.81	$61.80	$61.80
Purchase #5	$118.94	6.326%	$126.4641	$126.46	$126.45	$126.50
Purchase #6	$189.53	3.757%	$196.6506	$196.65	$196.65	$196.70
Purchase #7	$167.51	10.605%	$185.2744	$185.27	$185.25	$185.30
7 purchase totals =	$757.05		$810.1903	$810.18	$810.10	$810.30