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	$142.78	4.149%	$148.7039	$148.70	$148.70	$148.70
Purchase #2	$99.29	4.326%	$103.5853	$103.59	$103.60	$103.60
Purchase #3	$46.59	12.866%	$52.5843	$52.58	$52.60	$52.60
Purchase #4	$183.52	7.626%	$197.5152	$197.52	$197.50	$197.50
Purchase #5	$132.79	7.311%	$142.4983	$142.50	$142.50	$142.50
Purchase #6	$201.37	3.557%	$208.5327	$208.53	$208.55	$208.50
Purchase #7	$63.30	11.467%	$70.5586	$70.56	$70.55	$70.60
7 purchase totals =	$869.64		$923.9783	$923.98	$924.00	$924.00