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	$108.59	11.440%	$121.0127	$121.01	$121.00	$121.00
Purchase #2	$30.39	5.506%	$32.0633	$32.06	$32.05	$32.10
Purchase #3	$61.39	12.504%	$69.0662	$69.07	$69.05	$69.10
Purchase #4	$6.86	10.762%	$7.5983	$7.60	$7.60	$7.60
Purchase #5	$229.61	5.129%	$241.3867	$241.39	$241.40	$241.40
Purchase #6	$174.96	12.261%	$196.4118	$196.41	$196.40	$196.40
Purchase #7	$248.53	8.570%	$269.829	$269.83	$269.85	$269.80
7 purchase totals =	$860.33		$937.3680	$937.37	$937.35	$937.40