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	$63.34	12.603%	$71.3227	$71.32	$71.30	$71.30
Purchase #2	$235.56	8.392%	$255.3282	$255.33	$255.35	$255.30
Purchase #3	$85.40	4.178%	$88.968	$88.97	$88.95	$89.00
Purchase #4	$242.70	3.365%	$250.8669	$250.87	$250.85	$250.90
Purchase #5	$178.76	10.177%	$196.9524	$196.95	$196.95	$197.00
Purchase #6	$56.89	4.127%	$59.2379	$59.24	$59.25	$59.20
Purchase #7	$194.40	11.614%	$216.9776	$216.98	$217.00	$217.00
7 purchase totals =	$1,057.05		$1,139.6537	$1,139.66	$1,139.65	$1,139.70