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	$154.67	10.788%	$171.3558	$171.36	$171.35	$171.40
Purchase #2	$15.48	6.855%	$16.5412	$16.54	$16.55	$16.50
Purchase #3	$200.27	6.471%	$213.2295	$213.23	$213.25	$213.20
Purchase #4	$242.65	8.817%	$264.0445	$264.04	$264.05	$264.00
Purchase #5	$91.69	8.189%	$99.1985	$99.20	$99.20	$99.20
Purchase #6	$97.74	8.229%	$105.783	$105.78	$105.80	$105.80
Purchase #7	$84.40	6.568%	$89.9434	$89.94	$89.95	$89.90
7 purchase totals =	$886.90		$960.0959	$960.09	$960.15	$960.00