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	$189.70	10.348%	$209.3302	$209.33	$209.35	$209.30
Purchase #2	$103.37	13.872%	$117.7095	$117.71	$117.70	$117.70
Purchase #3	$233.83	12.647%	$263.4025	$263.40	$263.40	$263.40
Purchase #4	$20.30	5.239%	$21.3635	$21.36	$21.35	$21.40
Purchase #5	$158.95	12.640%	$179.0413	$179.04	$179.05	$179.00
Purchase #6	$43.92	5.857%	$46.4924	$46.49	$46.50	$46.50
Purchase #7	$155.64	5.863%	$164.7652	$164.77	$164.75	$164.80
7 purchase totals =	$905.71		$1,002.1046	$1,002.10	$1,002.10	$1,002.10