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	$99.88	9.547%	$109.4155	$109.42	$109.40	$109.40
Purchase #2	$227.38	8.739%	$247.2507	$247.25	$247.25	$247.30
Purchase #3	$50.70	8.321%	$54.9187	$54.92	$54.90	$54.90
Purchase #4	$91.29	9.473%	$99.9379	$99.94	$99.95	$99.90
Purchase #5	$63.96	7.575%	$68.805	$68.81	$68.80	$68.80
Purchase #6	$177.73	11.681%	$198.4906	$198.49	$198.50	$198.50
Purchase #7	$214.33	3.874%	$222.6331	$222.63	$222.65	$222.60
7 purchase totals =	$925.27		$1,001.4515	$1,001.46	$1,001.45	$1,001.40