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	$123.41	6.594%	$131.5477	$131.55	$131.55	$131.50
Purchase #2	$55.56	6.161%	$58.9831	$58.98	$59.00	$59.00
Purchase #3	$162.84	11.735%	$181.9493	$181.95	$181.95	$181.90
Purchase #4	$116.42	7.333%	$124.9571	$124.96	$124.95	$125.00
Purchase #5	$53.83	13.651%	$61.1783	$61.18	$61.20	$61.20
Purchase #6	$99.61	12.828%	$112.388	$112.39	$112.40	$112.40
Purchase #7	$229.29	3.593%	$237.5284	$237.53	$237.55	$237.50
7 purchase totals =	$840.96		$908.5319	$908.54	$908.60	$908.50