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	$108.92	6.573%	$116.0793	$116.08	$116.10	$116.10
Purchase #2	$238.30	12.759%	$268.7047	$268.70	$268.70	$268.70
Purchase #3	$31.45	13.801%	$35.7904	$35.79	$35.80	$35.80
Purchase #4	$141.88	7.329%	$152.2784	$152.28	$152.30	$152.30
Purchase #5	$192.60	3.809%	$199.9361	$199.94	$199.95	$199.90
Purchase #6	$39.77	7.572%	$42.7814	$42.78	$42.80	$42.80
Purchase #7	$219.48	3.603%	$227.3879	$227.39	$227.40	$227.40
7 purchase totals =	$972.40		$1,042.9582	$1,042.96	$1,043.05	$1,043.00