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	$126.89	3.656%	$131.5291	$131.53	$131.55	$131.50
Purchase #2	$162.28	11.583%	$181.0769	$181.08	$181.10	$181.10
Purchase #3	$157.33	7.849%	$169.6788	$169.68	$169.70	$169.70
Purchase #4	$74.73	10.542%	$82.608	$82.61	$82.60	$82.60
Purchase #5	$178.43	4.181%	$185.8902	$185.89	$185.90	$185.90
Purchase #6	$17.51	3.198%	$18.07	$18.07	$18.05	$18.10
Purchase #7	$245.44	12.220%	$275.4328	$275.43	$275.45	$275.40
7 purchase totals =	$962.61		$1,044.2858	$1,044.29	$1,044.35	$1,044.30