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	$240.95	11.407%	$268.4352	$268.44	$268.45	$268.40
Purchase #2	$160.87	3.140%	$165.9213	$165.92	$165.90	$165.90
Purchase #3	$5.46	11.451%	$6.0852	$6.09	$6.10	$6.10
Purchase #4	$208.72	3.460%	$215.9417	$215.94	$215.95	$215.90
Purchase #5	$151.56	8.580%	$164.5638	$164.56	$164.55	$164.60
Purchase #6	$58.71	13.636%	$66.7157	$66.72	$66.70	$66.70
Purchase #7	$215.96	11.410%	$240.601	$240.60	$240.60	$240.60
7 purchase totals =	$1,042.23		$1,128.2639	$1,128.27	$1,128.25	$1,128.20