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	$183.47	8.817%	$199.6465	$199.65	$199.65	$199.60
Purchase #2	$11.95	9.592%	$13.0962	$13.10	$13.10	$13.10
Purchase #3	$62.59	8.462%	$67.8864	$67.89	$67.90	$67.90
Purchase #4	$220.92	9.822%	$242.6188	$242.62	$242.60	$242.60
Purchase #5	$117.37	5.635%	$123.9838	$123.98	$124.00	$124.00
Purchase #6	$92.32	9.181%	$100.7959	$100.80	$100.80	$100.80
Purchase #7	$243.55	12.318%	$273.5505	$273.55	$273.55	$273.60
7 purchase totals =	$932.17		$1,021.5781	$1,021.59	$1,021.60	$1,021.60