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	$56.82	11.257%	$63.2162	$63.22	$63.20	$63.20
Purchase #2	$104.48	8.521%	$113.3827	$113.38	$113.40	$113.40
Purchase #3	$111.65	11.186%	$124.1392	$124.14	$124.15	$124.10
Purchase #4	$216.76	10.770%	$240.1051	$240.11	$240.10	$240.10
Purchase #5	$127.35	8.573%	$138.2677	$138.27	$138.25	$138.30
Purchase #6	$158.56	6.369%	$168.6587	$168.66	$168.65	$168.70
Purchase #7	$146.27	6.824%	$156.2515	$156.25	$156.25	$156.30
7 purchase totals =	$921.89		$1,004.0211	$1,004.03	$1,004.00	$1,004.10