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	$96.47	4.545%	$100.8546	$100.85	$100.85	$100.90
Purchase #2	$198.94	7.541%	$213.9421	$213.94	$213.95	$213.90
Purchase #3	$102.56	9.141%	$111.935	$111.94	$111.95	$111.90
Purchase #4	$101.68	11.300%	$113.1698	$113.17	$113.15	$113.20
Purchase #5	$61.88	12.842%	$69.8266	$69.83	$69.85	$69.80
Purchase #6	$158.99	10.752%	$176.0846	$176.08	$176.10	$176.10
Purchase #7	$6.34	5.461%	$6.6862	$6.69	$6.70	$6.70
7 purchase totals =	$726.86		$792.4989	$792.50	$792.55	$792.50