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	$47.98	9.696%	$52.6321	$52.63	$52.65	$52.60
Purchase #2	$222.83	11.794%	$249.1106	$249.11	$249.10	$249.10
Purchase #3	$207.43	5.165%	$218.1438	$218.14	$218.15	$218.10
Purchase #4	$31.76	5.440%	$33.4877	$33.49	$33.50	$33.50
Purchase #5	$140.81	10.249%	$155.2416	$155.24	$155.25	$155.20
Purchase #6	$51.49	5.496%	$54.3199	$54.32	$54.30	$54.30
Purchase #7	$11.92	13.441%	$13.5222	$13.52	$13.50	$13.50
7 purchase totals =	$714.22		$776.4579	$776.45	$776.45	$776.30