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	$83.90	13.835%	$95.5076	$95.51	$95.50	$95.50
Purchase #2	$16.61	11.602%	$18.5371	$18.54	$18.55	$18.50
Purchase #3	$196.40	3.818%	$203.8986	$203.90	$203.90	$203.90
Purchase #4	$101.84	7.438%	$109.4149	$109.41	$109.40	$109.40
Purchase #5	$30.27	13.537%	$34.3676	$34.37	$34.35	$34.40
Purchase #6	$111.33	12.242%	$124.959	$124.96	$124.95	$125.00
Purchase #7	$173.79	3.473%	$179.8257	$179.83	$179.85	$179.80
7 purchase totals =	$714.14		$766.5105	$766.52	$766.50	$766.50