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	$52.38	13.479%	$59.4403	$59.44	$59.45	$59.40
Purchase #2	$166.39	9.103%	$181.5365	$181.54	$181.55	$181.50
Purchase #3	$109.35	8.659%	$118.8186	$118.82	$118.80	$118.80
Purchase #4	$76.47	13.740%	$86.977	$86.98	$87.00	$87.00
Purchase #5	$82.96	8.219%	$89.7785	$89.78	$89.80	$89.80
Purchase #6	$235.40	8.564%	$255.5597	$255.56	$255.55	$255.60
Purchase #7	$54.72	12.643%	$61.6382	$61.64	$61.65	$61.60
7 purchase totals =	$777.67		$853.7488	$853.76	$853.80	$853.70