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	$198.94	5.185%	$209.255	$209.26	$209.25	$209.30
Purchase #2	$140.65	11.248%	$156.4703	$156.47	$156.45	$156.50
Purchase #3	$183.54	8.591%	$199.3079	$199.31	$199.30	$199.30
Purchase #4	$115.38	13.810%	$131.314	$131.31	$131.30	$131.30
Purchase #5	$34.68	10.612%	$38.3602	$38.36	$38.35	$38.40
Purchase #6	$206.80	9.400%	$226.2392	$226.24	$226.25	$226.20
Purchase #7	$128.87	8.566%	$139.909	$139.91	$139.90	$139.90
7 purchase totals =	$1,008.86		$1,100.8556	$1,100.86	$1,100.80	$1,100.90