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	$248.34	12.471%	$279.3105	$279.31	$279.30	$279.30
Purchase #2	$14.45	13.384%	$16.384	$16.38	$16.40	$16.40
Purchase #3	$99.50	9.856%	$109.3067	$109.31	$109.30	$109.30
Purchase #4	$31.27	5.155%	$32.882	$32.88	$32.90	$32.90
Purchase #5	$221.89	11.839%	$248.1596	$248.16	$248.15	$248.20
Purchase #6	$165.65	11.443%	$184.6053	$184.61	$184.60	$184.60
Purchase #7	$184.89	3.441%	$191.2521	$191.25	$191.25	$191.30
7 purchase totals =	$965.99		$1,061.9002	$1,061.90	$1,061.90	$1,062.00