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	$162.62	6.246%	$172.7772	$172.78	$172.80	$172.80
Purchase #2	$81.51	13.303%	$92.3533	$92.35	$92.35	$92.40
Purchase #3	$128.42	12.236%	$144.1335	$144.13	$144.15	$144.10
Purchase #4	$25.35	10.142%	$27.921	$27.92	$27.90	$27.90
Purchase #5	$161.96	10.845%	$179.5246	$179.52	$179.50	$179.50
Purchase #6	$144.61	7.197%	$155.0176	$155.02	$155.00	$155.00
Purchase #7	$163.86	7.196%	$175.6514	$175.65	$175.65	$175.70
7 purchase totals =	$868.33		$947.3786	$947.37	$947.35	$947.40