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	$128.25	10.218%	$141.3546	$141.35	$141.35	$141.40
Purchase #2	$34.40	12.293%	$38.6288	$38.63	$38.65	$38.60
Purchase #3	$129.88	4.474%	$135.6908	$135.69	$135.70	$135.70
Purchase #4	$22.57	13.520%	$25.6215	$25.62	$25.60	$25.60
Purchase #5	$33.91	11.826%	$37.9202	$37.92	$37.90	$37.90
Purchase #6	$173.88	4.571%	$181.8281	$181.83	$181.85	$181.80
Purchase #7	$124.67	5.492%	$131.5169	$131.52	$131.50	$131.50
7 purchase totals =	$647.56		$692.5609	$692.56	$692.55	$692.50