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	$181.76	6.426%	$193.4399	$193.44	$193.45	$193.40
Purchase #2	$88.55	13.490%	$100.4954	$100.50	$100.50	$100.50
Purchase #3	$78.50	3.221%	$81.0285	$81.03	$81.05	$81.00
Purchase #4	$94.45	11.607%	$105.4128	$105.41	$105.40	$105.40
Purchase #5	$250.68	6.347%	$266.5907	$266.59	$266.60	$266.60
Purchase #6	$193.41	7.464%	$207.8461	$207.85	$207.85	$207.80
Purchase #7	$123.75	6.548%	$131.8532	$131.85	$131.85	$131.90
7 purchase totals =	$1,011.10		$1,086.6666	$1,086.67	$1,086.70	$1,086.60