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	$93.37	5.189%	$98.215	$98.22	$98.20	$98.20
Purchase #2	$228.85	4.336%	$238.7729	$238.77	$238.75	$238.80
Purchase #3	$217.34	7.551%	$233.7513	$233.75	$233.75	$233.80
Purchase #4	$143.87	4.621%	$150.5182	$150.52	$150.50	$150.50
Purchase #5	$173.29	5.756%	$183.2646	$183.26	$183.25	$183.30
Purchase #6	$94.42	9.361%	$103.2587	$103.26	$103.25	$103.30
Purchase #7	$55.69	6.311%	$59.2046	$59.20	$59.20	$59.20
7 purchase totals =	$1,006.83		$1,066.9853	$1,066.98	$1,066.90	$1,067.10