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	$82.31	11.853%	$92.0662	$92.07	$92.05	$92.10
Purchase #2	$85.63	6.660%	$91.333	$91.33	$91.35	$91.30
Purchase #3	$72.70	6.783%	$77.6312	$77.63	$77.65	$77.60
Purchase #4	$14.82	13.625%	$16.8392	$16.84	$16.85	$16.80
Purchase #5	$180.78	11.139%	$200.9171	$200.92	$200.90	$200.90
Purchase #6	$94.97	5.170%	$99.8799	$99.88	$99.90	$99.90
Purchase #7	$178.82	6.245%	$189.9873	$189.99	$190.00	$190.00
7 purchase totals =	$710.03		$768.6539	$768.66	$768.70	$768.60