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	$215.81	11.550%	$240.7361	$240.74	$240.75	$240.70
Purchase #2	$109.34	7.178%	$117.1884	$117.19	$117.20	$117.20
Purchase #3	$83.97	5.694%	$88.7513	$88.75	$88.75	$88.80
Purchase #4	$215.85	9.138%	$235.5744	$235.57	$235.55	$235.60
Purchase #5	$187.94	4.571%	$196.5307	$196.53	$196.55	$196.50
Purchase #6	$168.28	10.400%	$185.7811	$185.78	$185.80	$185.80
Purchase #7	$20.82	7.354%	$22.3511	$22.35	$22.35	$22.40
7 purchase totals =	$1,002.01		$1,086.9131	$1,086.91	$1,086.95	$1,087.00