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	$117.65	6.526%	$125.3278	$125.33	$125.35	$125.30
Purchase #2	$27.31	4.761%	$28.6102	$28.61	$28.60	$28.60
Purchase #3	$37.93	13.316%	$42.9808	$42.98	$43.00	$43.00
Purchase #4	$31.49	7.707%	$33.9169	$33.92	$33.90	$33.90
Purchase #5	$45.50	11.255%	$50.621	$50.62	$50.60	$50.60
Purchase #6	$55.60	6.266%	$59.0839	$59.08	$59.10	$59.10
Purchase #7	$163.32	9.151%	$178.2654	$178.27	$178.25	$178.30
7 purchase totals =	$478.80		$518.8060	$518.81	$518.80	$518.80