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	$143.46	5.186%	$150.8998	$150.90	$150.90	$150.90
Purchase #2	$46.83	9.138%	$51.1093	$51.11	$51.10	$51.10
Purchase #3	$184.36	6.446%	$196.2438	$196.24	$196.25	$196.20
Purchase #4	$179.81	12.281%	$201.8925	$201.89	$201.90	$201.90
Purchase #5	$218.88	3.804%	$227.2062	$227.21	$227.20	$227.20
Purchase #6	$134.95	11.619%	$150.6298	$150.63	$150.65	$150.60
Purchase #7	$142.38	7.824%	$153.5198	$153.52	$153.50	$153.50
7 purchase totals =	$1,050.67		$1,131.5012	$1,131.50	$1,131.50	$1,131.40