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	$178.26	10.358%	$196.7242	$196.72	$196.70	$196.70
Purchase #2	$250.33	4.133%	$260.6761	$260.68	$260.70	$260.70
Purchase #3	$62.53	11.307%	$69.6003	$69.60	$69.60	$69.60
Purchase #4	$154.78	10.590%	$171.1712	$171.17	$171.15	$171.20
Purchase #5	$84.79	5.179%	$89.1813	$89.18	$89.20	$89.20
Purchase #6	$166.42	12.249%	$186.8048	$186.80	$186.80	$186.80
Purchase #7	$238.38	4.192%	$248.3729	$248.37	$248.35	$248.40
7 purchase totals =	$1,135.49		$1,222.5308	$1,222.52	$1,222.50	$1,222.60