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	$60.59	11.294%	$67.433	$67.43	$67.45	$67.40
Purchase #2	$89.79	8.194%	$97.1474	$97.15	$97.15	$97.10
Purchase #3	$21.55	10.801%	$23.8776	$23.88	$23.90	$23.90
Purchase #4	$38.82	9.280%	$42.4225	$42.42	$42.40	$42.40
Purchase #5	$53.84	3.675%	$55.8186	$55.82	$55.80	$55.80
Purchase #6	$26.94	9.176%	$29.412	$29.41	$29.40	$29.40
Purchase #7	$115.42	11.310%	$128.474	$128.47	$128.45	$128.50
7 purchase totals =	$406.95		$444.5851	$444.58	$444.55	$444.50