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	$57.30	3.434%	$59.2677	$59.27	$59.25	$59.30
Purchase #2	$35.80	12.342%	$40.2184	$40.22	$40.20	$40.20
Purchase #3	$233.34	8.822%	$253.9253	$253.93	$253.95	$253.90
Purchase #4	$204.26	7.171%	$218.9075	$218.91	$218.90	$218.90
Purchase #5	$32.83	11.309%	$36.5427	$36.54	$36.55	$36.50
Purchase #6	$40.44	7.265%	$43.378	$43.38	$43.40	$43.40
Purchase #7	$46.61	11.850%	$52.1333	$52.13	$52.15	$52.10
7 purchase totals =	$650.58		$704.3729	$704.38	$704.40	$704.30