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	$33.32	7.545%	$35.834	$35.83	$35.85	$35.80
Purchase #2	$20.53	4.718%	$21.4986	$21.50	$21.50	$21.50
Purchase #3	$53.29	7.405%	$57.2361	$57.24	$57.25	$57.20
Purchase #4	$228.49	11.761%	$255.3627	$255.36	$255.35	$255.40
Purchase #5	$233.95	6.770%	$249.7884	$249.79	$249.80	$249.80
Purchase #6	$37.66	8.550%	$40.8799	$40.88	$40.90	$40.90
Purchase #7	$104.96	8.301%	$113.6727	$113.67	$113.65	$113.70
7 purchase totals =	$712.20		$774.2724	$774.27	$774.30	$774.30