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	$96.53	9.244%	$105.4532	$105.45	$105.45	$105.50
Purchase #2	$146.51	11.631%	$163.5506	$163.55	$163.55	$163.60
Purchase #3	$67.79	5.512%	$71.5266	$71.53	$71.55	$71.50
Purchase #4	$40.92	6.134%	$43.43	$43.43	$43.45	$43.40
Purchase #5	$90.55	8.654%	$98.3862	$98.39	$98.40	$98.40
Purchase #6	$90.26	4.675%	$94.4797	$94.48	$94.50	$94.50
Purchase #7	$74.43	5.548%	$78.5594	$78.56	$78.55	$78.60
7 purchase totals =	$606.99		$655.3857	$655.39	$655.45	$655.50