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	$116.70	6.606%	$124.4092	$124.41	$124.40	$124.40
Purchase #2	$38.28	9.725%	$42.0027	$42.00	$42.00	$42.00
Purchase #3	$78.92	4.580%	$82.5345	$82.53	$82.55	$82.50
Purchase #4	$157.48	13.668%	$179.0044	$179.00	$179.00	$179.00
Purchase #5	$151.30	8.538%	$164.218	$164.22	$164.20	$164.20
Purchase #6	$223.28	6.406%	$237.5833	$237.58	$237.60	$237.60
Purchase #7	$207.89	9.814%	$228.2923	$228.29	$228.30	$228.30
7 purchase totals =	$973.85		$1,058.0444	$1,058.03	$1,058.05	$1,058.00