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	$140.45	8.642%	$152.5877	$152.59	$152.60	$152.60
Purchase #2	$171.25	6.556%	$182.4772	$182.48	$182.50	$182.50
Purchase #3	$199.64	9.432%	$218.47	$218.47	$218.45	$218.50
Purchase #4	$59.54	5.651%	$62.9046	$62.90	$62.90	$62.90
Purchase #5	$55.53	7.754%	$59.8358	$59.84	$59.85	$59.80
Purchase #6	$232.51	11.740%	$259.8067	$259.81	$259.80	$259.80
Purchase #7	$58.26	11.196%	$64.7828	$64.78	$64.80	$64.80
7 purchase totals =	$917.18		$1,000.8648	$1,000.87	$1,000.90	$1,000.90