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	$117.60	5.402%	$123.9528	$123.95	$123.95	$124.00
Purchase #2	$141.34	8.156%	$152.8677	$152.87	$152.85	$152.90
Purchase #3	$165.39	5.589%	$174.6336	$174.63	$174.65	$174.60
Purchase #4	$46.68	13.799%	$53.1214	$53.12	$53.10	$53.10
Purchase #5	$206.66	8.271%	$223.7528	$223.75	$223.75	$223.80
Purchase #6	$79.70	3.509%	$82.4967	$82.50	$82.50	$82.50
Purchase #7	$14.94	5.490%	$15.7602	$15.76	$15.75	$15.80
7 purchase totals =	$772.31		$826.5852	$826.58	$826.55	$826.70