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	$120.59	8.606%	$130.968	$130.97	$130.95	$131.00
Purchase #2	$176.57	11.359%	$196.6266	$196.63	$196.65	$196.60
Purchase #3	$108.35	4.674%	$113.4143	$113.41	$113.40	$113.40
Purchase #4	$176.46	10.701%	$195.343	$195.34	$195.35	$195.30
Purchase #5	$239.94	10.634%	$265.4552	$265.46	$265.45	$265.50
Purchase #6	$18.64	3.566%	$19.3047	$19.30	$19.30	$19.30
Purchase #7	$146.86	11.871%	$164.2938	$164.29	$164.30	$164.30
7 purchase totals =	$987.41		$1,085.4056	$1,085.40	$1,085.40	$1,085.40