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	$117.94	11.826%	$131.8876	$131.89	$131.90	$131.90
Purchase #2	$168.64	9.599%	$184.8278	$184.83	$184.85	$184.80
Purchase #3	$24.39	11.693%	$27.2419	$27.24	$27.25	$27.20
Purchase #4	$169.97	5.747%	$179.7382	$179.74	$179.75	$179.70
Purchase #5	$162.94	5.152%	$171.3347	$171.33	$171.35	$171.30
Purchase #6	$85.55	3.421%	$88.4767	$88.48	$88.50	$88.50
Purchase #7	$106.56	5.182%	$112.0819	$112.08	$112.10	$112.10
7 purchase totals =	$835.99		$895.5888	$895.59	$895.70	$895.50