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	$42.39	10.137%	$46.6871	$46.69	$46.70	$46.70
Purchase #2	$240.78	12.447%	$270.7499	$270.75	$270.75	$270.70
Purchase #3	$233.61	11.265%	$259.9262	$259.93	$259.95	$259.90
Purchase #4	$73.82	6.159%	$78.3666	$78.37	$78.35	$78.40
Purchase #5	$245.48	10.514%	$271.2898	$271.29	$271.30	$271.30
Purchase #6	$67.72	8.455%	$73.4457	$73.45	$73.45	$73.40
Purchase #7	$135.52	7.432%	$145.5918	$145.59	$145.60	$145.60
7 purchase totals =	$1,039.32		$1,146.0571	$1,146.07	$1,146.10	$1,146.00