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	$167.45	10.797%	$185.5296	$185.53	$185.55	$185.50
Purchase #2	$206.77	3.173%	$213.3308	$213.33	$213.35	$213.30
Purchase #3	$79.81	3.443%	$82.5579	$82.56	$82.55	$82.60
Purchase #4	$68.70	5.210%	$72.2793	$72.28	$72.30	$72.30
Purchase #5	$91.60	6.175%	$97.2563	$97.26	$97.25	$97.30
Purchase #6	$140.92	3.525%	$145.8874	$145.89	$145.90	$145.90
Purchase #7	$81.77	4.699%	$85.6124	$85.61	$85.60	$85.60
7 purchase totals =	$837.02		$882.4537	$882.46	$882.50	$882.50