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	$50.87	11.250%	$56.5929	$56.59	$56.60	$56.60
Purchase #2	$98.29	11.162%	$109.2611	$109.26	$109.25	$109.30
Purchase #3	$234.83	6.689%	$250.5378	$250.54	$250.55	$250.50
Purchase #4	$95.64	9.409%	$104.6388	$104.64	$104.65	$104.60
Purchase #5	$83.32	4.809%	$87.3269	$87.33	$87.35	$87.30
Purchase #6	$91.46	3.782%	$94.919	$94.92	$94.90	$94.90
Purchase #7	$29.41	6.403%	$31.2931	$31.29	$31.30	$31.30
7 purchase totals =	$683.82		$734.5696	$734.57	$734.60	$734.50