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	$13.43	6.702%	$14.3301	$14.33	$14.35	$14.30
Purchase #2	$119.51	7.791%	$128.821	$128.82	$128.80	$128.80
Purchase #3	$106.41	5.807%	$112.5892	$112.59	$112.60	$112.60
Purchase #4	$18.89	9.660%	$20.7148	$20.71	$20.70	$20.70
Purchase #5	$30.98	6.838%	$33.0984	$33.10	$33.10	$33.10
Purchase #6	$204.98	11.464%	$228.4789	$228.48	$228.50	$228.50
Purchase #7	$19.74	9.239%	$21.5638	$21.56	$21.55	$21.60
7 purchase totals =	$513.94		$559.5962	$559.59	$559.60	$559.60