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	$78.63	9.835%	$86.3633	$86.36	$86.35	$86.40
Purchase #2	$153.70	5.767%	$162.5639	$162.56	$162.55	$162.60
Purchase #3	$185.39	13.390%	$210.2137	$210.21	$210.20	$210.20
Purchase #4	$155.45	10.683%	$172.0567	$172.06	$172.05	$172.10
Purchase #5	$191.72	13.207%	$217.0405	$217.04	$217.05	$217.00
Purchase #6	$40.43	5.600%	$42.6941	$42.69	$42.70	$42.70
Purchase #7	$97.93	11.604%	$109.2938	$109.29	$109.30	$109.30
7 purchase totals =	$903.25		$1,000.2260	$1,000.21	$1,000.20	$1,000.30