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	$187.77	3.814%	$194.9315	$194.93	$194.95	$194.90
Purchase #2	$96.56	13.513%	$109.6082	$109.61	$109.60	$109.60
Purchase #3	$187.90	4.819%	$196.9549	$196.95	$196.95	$197.00
Purchase #4	$57.54	5.623%	$60.7755	$60.78	$60.80	$60.80
Purchase #5	$50.93	3.775%	$52.8526	$52.85	$52.85	$52.90
Purchase #6	$179.63	11.215%	$199.7755	$199.78	$199.80	$199.80
Purchase #7	$229.90	9.857%	$252.5612	$252.56	$252.55	$252.60
7 purchase totals =	$990.23		$1,067.4594	$1,067.46	$1,067.50	$1,067.60