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	$121.25	9.636%	$132.9337	$132.93	$132.95	$132.90
Purchase #2	$164.69	12.741%	$185.6732	$185.67	$185.65	$185.70
Purchase #3	$228.52	11.804%	$255.4945	$255.49	$255.50	$255.50
Purchase #4	$143.64	13.312%	$162.7614	$162.76	$162.75	$162.80
Purchase #5	$239.71	12.535%	$269.7576	$269.76	$269.75	$269.80
Purchase #6	$142.87	12.204%	$160.3059	$160.31	$160.30	$160.30
Purchase #7	$54.28	6.273%	$57.685	$57.69	$57.70	$57.70
7 purchase totals =	$1,094.96		$1,224.6113	$1,224.61	$1,224.60	$1,224.70