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	$55.86	8.209%	$60.4455	$60.45	$60.45	$60.40
Purchase #2	$76.37	12.110%	$85.6184	$85.62	$85.60	$85.60
Purchase #3	$116.53	12.379%	$130.9552	$130.96	$130.95	$131.00
Purchase #4	$135.85	3.832%	$141.0558	$141.06	$141.05	$141.10
Purchase #5	$190.68	4.172%	$198.6352	$198.64	$198.65	$198.60
Purchase #6	$55.60	7.487%	$59.7628	$59.76	$59.75	$59.80
Purchase #7	$189.90	13.502%	$215.5403	$215.54	$215.55	$215.50
7 purchase totals =	$820.79		$892.0132	$892.03	$892.00	$892.00