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	$201.65	10.222%	$222.2627	$222.26	$222.25	$222.30
Purchase #2	$110.33	12.195%	$123.7847	$123.78	$123.80	$123.80
Purchase #3	$140.69	5.779%	$148.8205	$148.82	$148.80	$148.80
Purchase #4	$85.80	11.311%	$95.5048	$95.50	$95.50	$95.50
Purchase #5	$224.58	3.645%	$232.7659	$232.77	$232.75	$232.80
Purchase #6	$189.38	5.121%	$199.0781	$199.08	$199.10	$199.10
Purchase #7	$156.31	11.615%	$174.4654	$174.47	$174.45	$174.50
7 purchase totals =	$1,108.74		$1,196.6821	$1,196.68	$1,196.65	$1,196.80