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	$243.90	6.792%	$260.4657	$260.47	$260.45	$260.50
Purchase #2	$71.33	10.582%	$78.8781	$78.88	$78.90	$78.90
Purchase #3	$111.31	4.180%	$115.9628	$115.96	$115.95	$116.00
Purchase #4	$184.48	5.266%	$194.1947	$194.19	$194.20	$194.20
Purchase #5	$43.78	3.347%	$45.2453	$45.25	$45.25	$45.20
Purchase #6	$227.55	9.739%	$249.7111	$249.71	$249.70	$249.70
Purchase #7	$169.92	5.344%	$179.0005	$179.00	$179.00	$179.00
7 purchase totals =	$1,052.27		$1,123.4582	$1,123.46	$1,123.45	$1,123.50