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	$238.37	7.774%	$256.9009	$256.90	$256.90	$256.90
Purchase #2	$195.99	12.508%	$220.5044	$220.50	$220.50	$220.50
Purchase #3	$206.34	12.154%	$231.4186	$231.42	$231.40	$231.40
Purchase #4	$53.83	11.268%	$59.8956	$59.90	$59.90	$59.90
Purchase #5	$38.56	3.355%	$39.8537	$39.85	$39.85	$39.90
Purchase #6	$132.89	11.461%	$148.1205	$148.12	$148.10	$148.10
Purchase #7	$166.31	10.853%	$184.3596	$184.36	$184.35	$184.40
7 purchase totals =	$1,032.29		$1,141.0533	$1,141.05	$1,141.00	$1,141.10