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	$139.80	9.233%	$152.7077	$152.71	$152.70	$152.70
Purchase #2	$107.76	9.302%	$117.7838	$117.78	$117.80	$117.80
Purchase #3	$139.94	7.811%	$150.8707	$150.87	$150.85	$150.90
Purchase #4	$196.94	3.654%	$204.1362	$204.14	$204.15	$204.10
Purchase #5	$192.91	8.214%	$208.7556	$208.76	$208.75	$208.80
Purchase #6	$21.38	5.278%	$22.5084	$22.51	$22.50	$22.50
Purchase #7	$242.66	13.147%	$274.5625	$274.56	$274.55	$274.60
7 purchase totals =	$1,041.39		$1,131.3249	$1,131.33	$1,131.30	$1,131.40