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	$11.26	9.139%	$12.2891	$12.29	$12.30	$12.30
Purchase #2	$124.91	5.150%	$131.3429	$131.34	$131.35	$131.30
Purchase #3	$250.41	4.805%	$262.4422	$262.44	$262.45	$262.40
Purchase #4	$250.26	13.537%	$284.1377	$284.14	$284.15	$284.10
Purchase #5	$30.89	12.844%	$34.8575	$34.86	$34.85	$34.90
Purchase #6	$213.93	9.592%	$234.4502	$234.45	$234.45	$234.50
Purchase #7	$46.36	10.685%	$51.3136	$51.31	$51.30	$51.30
7 purchase totals =	$928.02		$1,010.8332	$1,010.83	$1,010.85	$1,010.80