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	$128.43	10.477%	$141.8856	$141.89	$141.90	$141.90
Purchase #2	$199.94	3.740%	$207.4178	$207.42	$207.40	$207.40
Purchase #3	$97.95	9.773%	$107.5227	$107.52	$107.50	$107.50
Purchase #4	$241.61	3.592%	$250.2886	$250.29	$250.30	$250.30
Purchase #5	$82.53	10.208%	$90.9547	$90.95	$90.95	$91.00
Purchase #6	$97.51	12.619%	$109.8148	$109.81	$109.80	$109.80
Purchase #7	$128.85	9.250%	$140.7686	$140.77	$140.75	$140.80
7 purchase totals =	$976.82		$1,048.6528	$1,048.65	$1,048.60	$1,048.70