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	$60.70	8.279%	$65.7254	$65.73	$65.75	$65.70
Purchase #2	$100.62	11.832%	$112.5254	$112.53	$112.55	$112.50
Purchase #3	$99.82	4.559%	$104.3708	$104.37	$104.35	$104.40
Purchase #4	$82.86	11.496%	$92.3856	$92.39	$92.40	$92.40
Purchase #5	$81.82	12.382%	$91.951	$91.95	$91.95	$92.00
Purchase #6	$145.84	11.147%	$162.0968	$162.10	$162.10	$162.10
Purchase #7	$75.85	10.571%	$83.8681	$83.87	$83.85	$83.90
7 purchase totals =	$647.51		$712.9231	$712.94	$712.95	$713.00