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	$174.56	9.238%	$190.6859	$190.69	$190.70	$190.70
Purchase #2	$72.89	3.617%	$75.5264	$75.53	$75.55	$75.50
Purchase #3	$21.46	7.482%	$23.0656	$23.07	$23.05	$23.10
Purchase #4	$64.78	4.291%	$67.5597	$67.56	$67.55	$67.60
Purchase #5	$152.92	10.690%	$169.2671	$169.27	$169.25	$169.30
Purchase #6	$178.52	10.113%	$196.5737	$196.57	$196.55	$196.60
Purchase #7	$105.42	6.608%	$112.3862	$112.39	$112.40	$112.40
7 purchase totals =	$770.55		$835.0646	$835.08	$835.05	$835.20