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	$100.49	4.654%	$105.1668	$105.17	$105.15	$105.20
Purchase #2	$112.45	10.353%	$124.0919	$124.09	$124.10	$124.10
Purchase #3	$213.88	13.650%	$243.0746	$243.07	$243.05	$243.10
Purchase #4	$207.70	7.758%	$223.8134	$223.81	$223.80	$223.80
Purchase #5	$83.44	10.181%	$91.935	$91.94	$91.95	$91.90
Purchase #6	$244.78	5.724%	$258.7912	$258.79	$258.80	$258.80
Purchase #7	$11.55	4.372%	$12.055	$12.06	$12.05	$12.10
7 purchase totals =	$974.29		$1,058.9279	$1,058.93	$1,058.90	$1,059.00