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	$156.78	3.864%	$162.838	$162.84	$162.85	$162.80
Purchase #2	$39.93	13.536%	$45.3349	$45.33	$45.35	$45.30
Purchase #3	$245.63	11.333%	$273.4672	$273.47	$273.45	$273.50
Purchase #4	$127.78	5.369%	$134.6405	$134.64	$134.65	$134.60
Purchase #5	$219.82	6.676%	$234.4952	$234.50	$234.50	$234.50
Purchase #6	$174.55	12.552%	$196.4595	$196.46	$196.45	$196.50
Purchase #7	$20.59	11.720%	$23.0031	$23.00	$23.00	$23.00
7 purchase totals =	$985.08		$1,070.2384	$1,070.24	$1,070.25	$1,070.20