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	$74.94	8.512%	$81.3189	$81.32	$81.30	$81.30
Purchase #2	$198.45	8.804%	$215.9215	$215.92	$215.90	$215.90
Purchase #3	$113.87	10.238%	$125.528	$125.53	$125.55	$125.50
Purchase #4	$227.61	11.275%	$253.273	$253.27	$253.25	$253.30
Purchase #5	$107.61	3.346%	$111.2106	$111.21	$111.20	$111.20
Purchase #6	$193.42	9.567%	$211.9245	$211.92	$211.90	$211.90
Purchase #7	$16.87	7.590%	$18.1504	$18.15	$18.15	$18.20
7 purchase totals =	$932.77		$1,017.3269	$1,017.32	$1,017.25	$1,017.30