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	$43.44	5.133%	$45.6698	$45.67	$45.65	$45.70
Purchase #2	$50.86	10.769%	$56.3371	$56.34	$56.35	$56.30
Purchase #3	$121.55	8.276%	$131.6095	$131.61	$131.60	$131.60
Purchase #4	$115.82	6.739%	$123.6251	$123.63	$123.65	$123.60
Purchase #5	$128.40	6.398%	$136.615	$136.62	$136.60	$136.60
Purchase #6	$9.35	11.108%	$10.3886	$10.39	$10.40	$10.40
Purchase #7	$50.99	12.641%	$57.4356	$57.44	$57.45	$57.40
7 purchase totals =	$520.41		$561.6807	$561.70	$561.70	$561.60