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	$93.91	11.717%	$104.9134	$104.91	$104.90	$104.90
Purchase #2	$88.65	9.735%	$97.2801	$97.28	$97.30	$97.30
Purchase #3	$31.29	6.341%	$33.2741	$33.27	$33.25	$33.30
Purchase #4	$88.78	12.698%	$100.0533	$100.05	$100.05	$100.10
Purchase #5	$114.31	3.370%	$118.1622	$118.16	$118.15	$118.20
Purchase #6	$6.51	7.726%	$7.013	$7.01	$7.00	$7.00
Purchase #7	$155.46	8.269%	$168.315	$168.32	$168.30	$168.30
7 purchase totals =	$578.91		$629.0111	$629.00	$628.95	$629.10