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	$63.94	11.786%	$71.476	$71.48	$71.50	$71.50
Purchase #2	$249.71	5.144%	$262.5551	$262.56	$262.55	$262.60
Purchase #3	$223.77	13.861%	$254.7868	$254.79	$254.80	$254.80
Purchase #4	$41.54	4.374%	$43.357	$43.36	$43.35	$43.40
Purchase #5	$40.52	7.252%	$43.4585	$43.46	$43.45	$43.50
Purchase #6	$131.68	7.601%	$141.689	$141.69	$141.70	$141.70
Purchase #7	$8.48	7.647%	$9.1285	$9.13	$9.15	$9.10
7 purchase totals =	$759.64		$826.4509	$826.47	$826.50	$826.60