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	$161.56	6.301%	$171.7399	$171.74	$171.75	$171.70
Purchase #2	$151.60	5.286%	$159.6136	$159.61	$159.60	$159.60
Purchase #3	$103.86	12.571%	$116.9162	$116.92	$116.90	$116.90
Purchase #4	$164.64	11.426%	$183.4518	$183.45	$183.45	$183.50
Purchase #5	$193.42	8.270%	$209.4158	$209.42	$209.40	$209.40
Purchase #6	$97.30	11.529%	$108.5177	$108.52	$108.50	$108.50
Purchase #7	$48.25	6.488%	$51.3805	$51.38	$51.40	$51.40
7 purchase totals =	$920.63		$1,001.0355	$1,001.04	$1,001.00	$1,001.00