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	$117.34	12.336%	$131.8151	$131.82	$131.80	$131.80
Purchase #2	$180.60	5.266%	$190.1104	$190.11	$190.10	$190.10
Purchase #3	$184.37	8.464%	$199.9751	$199.98	$200.00	$200.00
Purchase #4	$191.30	4.616%	$200.1304	$200.13	$200.15	$200.10
Purchase #5	$237.70	12.435%	$267.258	$267.26	$267.25	$267.30
Purchase #6	$88.46	3.533%	$91.5853	$91.59	$91.60	$91.60
Purchase #7	$90.36	9.504%	$98.9478	$98.95	$98.95	$98.90
7 purchase totals =	$1,090.13		$1,179.8221	$1,179.84	$1,179.85	$1,179.80