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	$221.69	12.142%	$248.6076	$248.61	$248.60	$248.60
Purchase #2	$212.62	4.546%	$222.2857	$222.29	$222.30	$222.30
Purchase #3	$233.47	10.541%	$258.0801	$258.08	$258.10	$258.10
Purchase #4	$240.37	10.454%	$265.4983	$265.50	$265.50	$265.50
Purchase #5	$162.76	5.426%	$171.5914	$171.59	$171.60	$171.60
Purchase #6	$164.66	8.611%	$178.8389	$178.84	$178.85	$178.80
Purchase #7	$66.94	7.826%	$72.1787	$72.18	$72.20	$72.20
7 purchase totals =	$1,302.51		$1,417.0807	$1,417.09	$1,417.15	$1,417.10