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	$49.96	11.258%	$55.5845	$55.58	$55.60	$55.60
Purchase #2	$159.98	4.231%	$166.7488	$166.75	$166.75	$166.70
Purchase #3	$231.76	7.293%	$248.6623	$248.66	$248.65	$248.70
Purchase #4	$91.76	7.211%	$98.3768	$98.38	$98.40	$98.40
Purchase #5	$80.86	5.686%	$85.4577	$85.46	$85.45	$85.50
Purchase #6	$181.91	9.143%	$198.542	$198.54	$198.55	$198.50
Purchase #7	$81.49	11.680%	$91.008	$91.01	$91.00	$91.00
7 purchase totals =	$877.72		$944.3801	$944.38	$944.40	$944.40