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	$153.39	10.357%	$169.2766	$169.28	$169.30	$169.30
Purchase #2	$101.50	7.369%	$108.9795	$108.98	$109.00	$109.00
Purchase #3	$208.50	12.480%	$234.5208	$234.52	$234.50	$234.50
Purchase #4	$91.90	13.705%	$104.4949	$104.49	$104.50	$104.50
Purchase #5	$149.50	10.789%	$165.6296	$165.63	$165.65	$165.60
Purchase #6	$175.25	6.150%	$186.0279	$186.03	$186.05	$186.00
Purchase #7	$37.90	12.301%	$42.5621	$42.56	$42.55	$42.60
7 purchase totals =	$917.94		$1,011.4914	$1,011.49	$1,011.55	$1,011.50