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	$43.34	10.344%	$47.8231	$47.82	$47.80	$47.80
Purchase #2	$222.56	6.382%	$236.7638	$236.76	$236.75	$236.80
Purchase #3	$73.44	13.792%	$83.5688	$83.57	$83.55	$83.60
Purchase #4	$81.33	5.322%	$85.6584	$85.66	$85.65	$85.70
Purchase #5	$180.84	7.236%	$193.9256	$193.93	$193.95	$193.90
Purchase #6	$112.31	13.778%	$127.7841	$127.78	$127.80	$127.80
Purchase #7	$91.52	3.317%	$94.5557	$94.56	$94.55	$94.60
7 purchase totals =	$805.34		$870.0795	$870.08	$870.05	$870.20