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	$152.48	12.687%	$171.8251	$171.83	$171.85	$171.80
Purchase #2	$243.51	12.320%	$273.5104	$273.51	$273.50	$273.50
Purchase #3	$178.44	11.683%	$199.2871	$199.29	$199.30	$199.30
Purchase #4	$226.29	10.709%	$250.5234	$250.52	$250.50	$250.50
Purchase #5	$188.89	6.659%	$201.4682	$201.47	$201.45	$201.50
Purchase #6	$24.52	12.250%	$27.5237	$27.52	$27.50	$27.50
Purchase #7	$39.33	12.681%	$44.3174	$44.32	$44.30	$44.30
7 purchase totals =	$1,053.46		$1,168.4553	$1,168.46	$1,168.40	$1,168.40