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	$161.92	6.102%	$171.8004	$171.80	$171.80	$171.80
Purchase #2	$72.60	13.387%	$82.319	$82.32	$82.30	$82.30
Purchase #3	$216.81	8.695%	$235.6616	$235.66	$235.65	$235.70
Purchase #4	$38.42	13.539%	$43.6217	$43.62	$43.60	$43.60
Purchase #5	$246.77	8.327%	$267.3185	$267.32	$267.30	$267.30
Purchase #6	$96.45	4.585%	$100.8722	$100.87	$100.85	$100.90
Purchase #7	$124.71	7.383%	$133.9173	$133.92	$133.90	$133.90
7 purchase totals =	$957.68		$1,035.5107	$1,035.51	$1,035.40	$1,035.50