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	$197.89	4.338%	$206.4745	$206.47	$206.45	$206.50
Purchase #2	$57.42	7.515%	$61.7351	$61.74	$61.75	$61.70
Purchase #3	$127.60	3.110%	$131.5684	$131.57	$131.55	$131.60
Purchase #4	$174.93	3.710%	$181.4199	$181.42	$181.40	$181.40
Purchase #5	$211.70	13.179%	$239.5999	$239.60	$239.60	$239.60
Purchase #6	$171.59	5.561%	$181.1321	$181.13	$181.15	$181.10
Purchase #7	$56.27	11.801%	$62.9104	$62.91	$62.90	$62.90
7 purchase totals =	$997.40		$1,064.8403	$1,064.84	$1,064.80	$1,064.80