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	$230.31	4.662%	$241.0471	$241.05	$241.05	$241.00
Purchase #2	$76.45	3.865%	$79.4048	$79.40	$79.40	$79.40
Purchase #3	$81.88	13.495%	$92.9297	$92.93	$92.95	$92.90
Purchase #4	$58.61	6.718%	$62.5474	$62.55	$62.55	$62.50
Purchase #5	$109.77	6.503%	$116.9083	$116.91	$116.90	$116.90
Purchase #6	$27.59	13.848%	$31.4107	$31.41	$31.40	$31.40
Purchase #7	$83.54	7.379%	$89.7044	$89.70	$89.70	$89.70
7 purchase totals =	$668.15		$713.9524	$713.95	$713.95	$713.80