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	$134.66	7.270%	$144.4498	$144.45	$144.45	$144.40
Purchase #2	$179.27	9.665%	$196.5964	$196.60	$196.60	$196.60
Purchase #3	$36.35	13.830%	$41.3772	$41.38	$41.40	$41.40
Purchase #4	$5.60	9.831%	$6.1505	$6.15	$6.15	$6.20
Purchase #5	$85.32	8.545%	$92.6106	$92.61	$92.60	$92.60
Purchase #6	$134.58	5.411%	$141.8621	$141.86	$141.85	$141.90
Purchase #7	$133.94	10.143%	$147.5255	$147.53	$147.55	$147.50
7 purchase totals =	$709.72		$770.5721	$770.58	$770.60	$770.60