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	$143.35	13.167%	$162.2249	$162.22	$162.20	$162.20
Purchase #2	$128.65	6.811%	$137.4124	$137.41	$137.40	$137.40
Purchase #3	$230.83	7.552%	$248.2623	$248.26	$248.25	$248.30
Purchase #4	$180.26	3.280%	$186.1725	$186.17	$186.15	$186.20
Purchase #5	$80.58	11.501%	$89.8475	$89.85	$89.85	$89.80
Purchase #6	$222.34	5.321%	$234.1707	$234.17	$234.15	$234.20
Purchase #7	$60.33	11.682%	$67.3778	$67.38	$67.40	$67.40
7 purchase totals =	$1,046.34		$1,125.4681	$1,125.46	$1,125.40	$1,125.50