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	$184.53	6.705%	$196.9027	$196.90	$196.90	$196.90
Purchase #2	$136.31	6.169%	$144.719	$144.72	$144.70	$144.70
Purchase #3	$157.71	4.860%	$165.3747	$165.37	$165.35	$165.40
Purchase #4	$168.50	12.700%	$189.8995	$189.90	$189.90	$189.90
Purchase #5	$208.67	9.261%	$227.9949	$227.99	$228.00	$228.00
Purchase #6	$171.27	3.140%	$176.6479	$176.65	$176.65	$176.60
Purchase #7	$77.76	6.698%	$82.9684	$82.97	$82.95	$83.00
7 purchase totals =	$1,104.75		$1,184.5071	$1,184.50	$1,184.45	$1,184.50