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	$108.28	8.384%	$117.3582	$117.36	$117.35	$117.40
Purchase #2	$29.72	10.521%	$32.8468	$32.85	$32.85	$32.80
Purchase #3	$207.62	10.559%	$229.5426	$229.54	$229.55	$229.50
Purchase #4	$241.76	12.281%	$271.4505	$271.45	$271.45	$271.50
Purchase #5	$5.47	6.202%	$5.8092	$5.81	$5.80	$5.80
Purchase #6	$160.61	10.156%	$176.9216	$176.92	$176.90	$176.90
Purchase #7	$170.93	6.661%	$182.3156	$182.32	$182.30	$182.30
7 purchase totals =	$924.39		$1,016.2445	$1,016.25	$1,016.20	$1,016.20