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	$86.31	3.382%	$89.229	$89.23	$89.25	$89.20
Purchase #2	$59.26	7.283%	$63.5759	$63.58	$63.60	$63.60
Purchase #3	$166.73	10.439%	$184.1349	$184.13	$184.15	$184.10
Purchase #4	$107.96	3.812%	$112.0754	$112.08	$112.10	$112.10
Purchase #5	$88.47	8.111%	$95.6458	$95.65	$95.65	$95.60
Purchase #6	$65.59	12.167%	$73.5703	$73.57	$73.55	$73.60
Purchase #7	$136.95	10.467%	$151.2846	$151.28	$151.30	$151.30
7 purchase totals =	$711.27		$769.5159	$769.52	$769.60	$769.50