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	$182.91	4.158%	$190.5154	$190.52	$190.50	$190.50
Purchase #2	$153.99	12.628%	$173.4359	$173.44	$173.45	$173.40
Purchase #3	$224.49	10.582%	$248.2455	$248.25	$248.25	$248.20
Purchase #4	$161.53	11.170%	$179.5729	$179.57	$179.55	$179.60
Purchase #5	$110.75	3.439%	$114.5587	$114.56	$114.55	$114.60
Purchase #6	$49.31	11.448%	$54.955	$54.96	$54.95	$55.00
Purchase #7	$134.48	13.732%	$152.9468	$152.95	$152.95	$152.90
7 purchase totals =	$1,017.46		$1,114.2302	$1,114.25	$1,114.20	$1,114.20