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	$214.37	4.272%	$223.5279	$223.53	$223.55	$223.50
Purchase #2	$136.71	7.424%	$146.8594	$146.86	$146.85	$146.90
Purchase #3	$148.84	5.139%	$156.4889	$156.49	$156.50	$156.50
Purchase #4	$209.56	7.153%	$224.5498	$224.55	$224.55	$224.50
Purchase #5	$170.54	4.571%	$178.3354	$178.34	$178.35	$178.30
Purchase #6	$79.46	12.691%	$89.5443	$89.54	$89.55	$89.50
Purchase #7	$248.35	3.829%	$257.8593	$257.86	$257.85	$257.90
7 purchase totals =	$1,207.83		$1,277.1650	$1,277.17	$1,277.20	$1,277.10