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	$208.36	8.818%	$226.7332	$226.73	$226.75	$226.70
Purchase #2	$32.64	12.303%	$36.6557	$36.66	$36.65	$36.70
Purchase #3	$78.47	4.553%	$82.0427	$82.04	$82.05	$82.00
Purchase #4	$44.86	12.433%	$50.4374	$50.44	$50.45	$50.40
Purchase #5	$240.88	10.405%	$265.9436	$265.94	$265.95	$265.90
Purchase #6	$215.47	13.857%	$245.3277	$245.33	$245.35	$245.30
Purchase #7	$97.35	3.118%	$100.3854	$100.39	$100.40	$100.40
7 purchase totals =	$918.03		$1,007.5257	$1,007.53	$1,007.60	$1,007.40