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	$208.77	9.601%	$228.814	$228.81	$228.80	$228.80
Purchase #2	$103.67	11.858%	$115.9632	$115.96	$115.95	$116.00
Purchase #3	$158.53	13.399%	$179.7714	$179.77	$179.75	$179.80
Purchase #4	$43.53	4.660%	$45.5585	$45.56	$45.55	$45.60
Purchase #5	$177.34	4.179%	$184.751	$184.75	$184.75	$184.80
Purchase #6	$179.55	6.736%	$191.6445	$191.64	$191.65	$191.60
Purchase #7	$140.27	3.639%	$145.3744	$145.37	$145.35	$145.40
7 purchase totals =	$1,011.66		$1,091.8770	$1,091.86	$1,091.80	$1,092.00