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	$157.37	11.468%	$175.4172	$175.42	$175.40	$175.40
Purchase #2	$56.78	8.395%	$61.5467	$61.55	$61.55	$61.50
Purchase #3	$150.86	13.461%	$171.1673	$171.17	$171.15	$171.20
Purchase #4	$80.66	8.218%	$87.2886	$87.29	$87.30	$87.30
Purchase #5	$119.87	7.539%	$128.907	$128.91	$128.90	$128.90
Purchase #6	$31.35	3.833%	$32.5516	$32.55	$32.55	$32.60
Purchase #7	$177.41	5.704%	$187.5295	$187.53	$187.55	$187.50
7 purchase totals =	$774.30		$844.4079	$844.42	$844.40	$844.40