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	$118.37	4.809%	$124.0624	$124.06	$124.05	$124.10
Purchase #2	$214.50	4.339%	$223.8072	$223.81	$223.80	$223.80
Purchase #3	$237.91	10.800%	$263.6043	$263.60	$263.60	$263.60
Purchase #4	$135.78	9.446%	$148.6058	$148.61	$148.60	$148.60
Purchase #5	$226.27	7.546%	$243.3443	$243.34	$243.35	$243.30
Purchase #6	$52.49	10.297%	$57.8949	$57.89	$57.90	$57.90
Purchase #7	$9.84	13.709%	$11.189	$11.19	$11.20	$11.20
7 purchase totals =	$995.16		$1,072.5079	$1,072.50	$1,072.50	$1,072.50