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	$166.82	7.478%	$179.2948	$179.29	$179.30	$179.30
Purchase #2	$66.88	3.597%	$69.2857	$69.29	$69.30	$69.30
Purchase #3	$51.45	4.731%	$53.8841	$53.88	$53.90	$53.90
Purchase #4	$201.27	10.535%	$222.4738	$222.47	$222.45	$222.50
Purchase #5	$141.27	11.272%	$157.194	$157.19	$157.20	$157.20
Purchase #6	$141.32	6.649%	$150.7164	$150.72	$150.70	$150.70
Purchase #7	$249.32	13.784%	$283.6863	$283.69	$283.70	$283.70
7 purchase totals =	$1,018.33		$1,116.5351	$1,116.53	$1,116.55	$1,116.60