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	$77.70	11.480%	$86.62	$86.62	$86.60	$86.60
Purchase #2	$33.56	12.582%	$37.7825	$37.78	$37.80	$37.80
Purchase #3	$136.57	8.795%	$148.5813	$148.58	$148.60	$148.60
Purchase #4	$51.37	10.408%	$56.7166	$56.72	$56.70	$56.70
Purchase #5	$153.56	7.286%	$164.7484	$164.75	$164.75	$164.70
Purchase #6	$89.56	9.584%	$98.1434	$98.14	$98.15	$98.10
Purchase #7	$248.92	6.631%	$265.4259	$265.43	$265.45	$265.40
7 purchase totals =	$791.24		$858.0181	$858.02	$858.05	$857.90