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	$151.91	4.571%	$158.8538	$158.85	$158.85	$158.90
Purchase #2	$94.64	11.772%	$105.781	$105.78	$105.80	$105.80
Purchase #3	$125.84	13.528%	$142.8636	$142.86	$142.85	$142.90
Purchase #4	$19.38	13.501%	$21.9965	$22.00	$22.00	$22.00
Purchase #5	$191.78	4.614%	$200.6287	$200.63	$200.65	$200.60
Purchase #6	$99.55	5.372%	$104.8978	$104.90	$104.90	$104.90
Purchase #7	$16.42	11.732%	$18.3464	$18.35	$18.35	$18.30
7 purchase totals =	$699.52		$753.3678	$753.37	$753.40	$753.40