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	$248.84	10.613%	$275.2494	$275.25	$275.25	$275.20
Purchase #2	$103.95	12.160%	$116.5903	$116.59	$116.60	$116.60
Purchase #3	$187.85	5.839%	$198.8186	$198.82	$198.80	$198.80
Purchase #4	$220.70	8.217%	$238.8349	$238.83	$238.85	$238.80
Purchase #5	$57.64	11.658%	$64.3597	$64.36	$64.35	$64.40
Purchase #6	$99.98	5.578%	$105.5569	$105.56	$105.55	$105.60
Purchase #7	$161.26	4.544%	$168.5877	$168.59	$168.60	$168.60
7 purchase totals =	$1,080.22		$1,167.9975	$1,168.00	$1,168.00	$1,168.00