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	$48.47	7.375%	$52.0447	$52.04	$52.05	$52.00
Purchase #2	$211.30	13.242%	$239.2803	$239.28	$239.30	$239.30
Purchase #3	$40.33	12.854%	$45.514	$45.51	$45.50	$45.50
Purchase #4	$219.33	6.435%	$233.4439	$233.44	$233.45	$233.40
Purchase #5	$208.90	5.370%	$220.1179	$220.12	$220.10	$220.10
Purchase #6	$52.59	13.196%	$59.5298	$59.53	$59.55	$59.50
Purchase #7	$15.88	4.173%	$16.5427	$16.54	$16.55	$16.50
7 purchase totals =	$796.80		$866.4733	$866.46	$866.50	$866.30