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	$205.54	5.809%	$217.4798	$217.48	$217.50	$217.50
Purchase #2	$89.46	12.535%	$100.6738	$100.67	$100.65	$100.70
Purchase #3	$218.73	5.805%	$231.4273	$231.43	$231.45	$231.40
Purchase #4	$250.30	4.372%	$261.2431	$261.24	$261.25	$261.20
Purchase #5	$235.58	7.740%	$253.8139	$253.81	$253.80	$253.80
Purchase #6	$41.46	9.453%	$45.3792	$45.38	$45.40	$45.40
Purchase #7	$109.50	6.689%	$116.8245	$116.82	$116.80	$116.80
7 purchase totals =	$1,150.57		$1,226.8416	$1,226.83	$1,226.85	$1,226.80