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	$73.86	10.499%	$81.6146	$81.61	$81.60	$81.60
Purchase #2	$112.27	10.266%	$123.7956	$123.80	$123.80	$123.80
Purchase #3	$86.34	10.767%	$95.6362	$95.64	$95.65	$95.60
Purchase #4	$126.93	11.110%	$141.0319	$141.03	$141.05	$141.00
Purchase #5	$79.66	3.448%	$82.4067	$82.41	$82.40	$82.40
Purchase #6	$23.72	5.470%	$25.0175	$25.02	$25.00	$25.00
Purchase #7	$41.32	4.162%	$43.0397	$43.04	$43.05	$43.00
7 purchase totals =	$544.10		$592.5422	$592.55	$592.55	$592.40