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	$134.71	11.500%	$150.2017	$150.20	$150.20	$150.20
Purchase #2	$185.80	12.354%	$208.7537	$208.75	$208.75	$208.80
Purchase #3	$184.44	13.270%	$208.9152	$208.92	$208.90	$208.90
Purchase #4	$179.63	9.568%	$196.817	$196.82	$196.80	$196.80
Purchase #5	$93.46	12.261%	$104.9191	$104.92	$104.90	$104.90
Purchase #6	$165.27	4.336%	$172.4361	$172.44	$172.45	$172.40
Purchase #7	$120.85	8.855%	$131.5513	$131.55	$131.55	$131.60
7 purchase totals =	$1,064.16		$1,173.5941	$1,173.60	$1,173.55	$1,173.60