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	$93.90	3.585%	$97.2663	$97.27	$97.25	$97.30
Purchase #2	$18.78	8.779%	$20.4287	$20.43	$20.45	$20.40
Purchase #3	$149.54	12.110%	$167.6493	$167.65	$167.65	$167.60
Purchase #4	$95.40	11.700%	$106.5618	$106.56	$106.55	$106.60
Purchase #5	$174.53	3.181%	$180.0818	$180.08	$180.10	$180.10
Purchase #6	$73.39	12.318%	$82.4302	$82.43	$82.45	$82.40
Purchase #7	$84.27	6.833%	$90.0282	$90.03	$90.05	$90.00
7 purchase totals =	$689.81		$744.4463	$744.45	$744.50	$744.40