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	$91.41	11.234%	$101.679	$101.68	$101.70	$101.70
Purchase #2	$76.42	7.507%	$82.1568	$82.16	$82.15	$82.20
Purchase #3	$38.86	9.432%	$42.5253	$42.53	$42.55	$42.50
Purchase #4	$241.27	10.256%	$266.0147	$266.01	$266.00	$266.00
Purchase #5	$29.92	5.573%	$31.5874	$31.59	$31.60	$31.60
Purchase #6	$19.72	11.758%	$22.0387	$22.04	$22.05	$22.00
Purchase #7	$47.52	10.188%	$52.3613	$52.36	$52.35	$52.40
7 purchase totals =	$545.12		$598.3632	$598.37	$598.40	$598.40