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	$100.93	4.265%	$105.2347	$105.23	$105.25	$105.20
Purchase #2	$24.82	10.191%	$27.3494	$27.35	$27.35	$27.30
Purchase #3	$191.30	10.764%	$211.8915	$211.89	$211.90	$211.90
Purchase #4	$104.59	12.136%	$117.283	$117.28	$117.30	$117.30
Purchase #5	$214.26	13.660%	$243.5279	$243.53	$243.55	$243.50
Purchase #6	$219.27	13.781%	$249.4876	$249.49	$249.50	$249.50
Purchase #7	$46.32	12.619%	$52.1651	$52.17	$52.15	$52.20
7 purchase totals =	$901.49		$1,006.9392	$1,006.94	$1,007.00	$1,006.90