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	$183.30	3.475%	$189.6697	$189.67	$189.65	$189.70
Purchase #2	$225.28	10.718%	$249.4255	$249.43	$249.45	$249.40
Purchase #3	$169.87	9.653%	$186.2676	$186.27	$186.25	$186.30
Purchase #4	$80.43	11.359%	$89.566	$89.57	$89.55	$89.60
Purchase #5	$19.93	4.600%	$20.8468	$20.85	$20.85	$20.80
Purchase #6	$24.31	4.143%	$25.3172	$25.32	$25.30	$25.30
Purchase #7	$250.59	12.614%	$282.1994	$282.20	$282.20	$282.20
7 purchase totals =	$953.71		$1,043.2922	$1,043.31	$1,043.25	$1,043.30