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	$130.73	5.289%	$137.6443	$137.64	$137.65	$137.60
Purchase #2	$128.36	13.214%	$145.3215	$145.32	$145.30	$145.30
Purchase #3	$143.52	4.864%	$150.5008	$150.50	$150.50	$150.50
Purchase #4	$73.79	6.719%	$78.748	$78.75	$78.75	$78.70
Purchase #5	$190.83	12.709%	$215.0826	$215.08	$215.10	$215.10
Purchase #6	$217.91	5.483%	$229.858	$229.86	$229.85	$229.90
Purchase #7	$58.40	7.825%	$62.9698	$62.97	$62.95	$63.00
7 purchase totals =	$943.54		$1,020.1250	$1,020.12	$1,020.10	$1,020.10