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	$146.93	6.628%	$156.6685	$156.67	$156.65	$156.70
Purchase #2	$94.28	5.523%	$99.4871	$99.49	$99.50	$99.50
Purchase #3	$90.46	4.480%	$94.5126	$94.51	$94.50	$94.50
Purchase #4	$241.40	12.184%	$270.8122	$270.81	$270.80	$270.80
Purchase #5	$107.45	13.307%	$121.7484	$121.75	$121.75	$121.70
Purchase #6	$239.53	10.319%	$264.2471	$264.25	$264.25	$264.20
Purchase #7	$171.32	4.211%	$178.5343	$178.53	$178.55	$178.50
7 purchase totals =	$1,091.37		$1,186.0102	$1,186.01	$1,186.00	$1,185.90