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	$36.87	4.768%	$38.628	$38.63	$38.65	$38.60
Purchase #2	$72.43	12.278%	$81.323	$81.32	$81.30	$81.30
Purchase #3	$11.89	6.858%	$12.7054	$12.71	$12.70	$12.70
Purchase #4	$49.93	6.678%	$53.2643	$53.26	$53.25	$53.30
Purchase #5	$36.54	3.605%	$37.8573	$37.86	$37.85	$37.90
Purchase #6	$105.30	3.644%	$109.1371	$109.14	$109.15	$109.10
Purchase #7	$128.60	10.130%	$141.6272	$141.63	$141.65	$141.60
7 purchase totals =	$441.56		$474.5423	$474.55	$474.55	$474.50