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	$20.98	5.252%	$22.0819	$22.08	$22.10	$22.10
Purchase #2	$171.32	3.451%	$177.2323	$177.23	$177.25	$177.20
Purchase #3	$208.42	7.181%	$223.3866	$223.39	$223.40	$223.40
Purchase #4	$167.25	6.740%	$178.5227	$178.52	$178.50	$178.50
Purchase #5	$121.33	8.392%	$131.512	$131.51	$131.50	$131.50
Purchase #6	$100.87	4.107%	$105.0127	$105.01	$105.00	$105.00
Purchase #7	$43.87	10.736%	$48.5799	$48.58	$48.60	$48.60
7 purchase totals =	$834.04		$886.3281	$886.32	$886.35	$886.30