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	$42.63	4.468%	$44.5347	$44.53	$44.55	$44.50
Purchase #2	$135.30	4.650%	$141.5915	$141.59	$141.60	$141.60
Purchase #3	$126.61	13.256%	$143.3934	$143.39	$143.40	$143.40
Purchase #4	$110.64	7.822%	$119.2943	$119.29	$119.30	$119.30
Purchase #5	$79.75	12.684%	$89.8655	$89.87	$89.85	$89.90
Purchase #6	$102.89	3.450%	$106.4397	$106.44	$106.45	$106.40
Purchase #7	$28.95	10.609%	$32.0213	$32.02	$32.00	$32.00
7 purchase totals =	$626.77		$677.1404	$677.13	$677.15	$677.10