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	$218.51	3.661%	$226.5097	$226.51	$226.50	$226.50
Purchase #2	$233.31	6.360%	$248.1485	$248.15	$248.15	$248.10
Purchase #3	$20.73	4.353%	$21.6324	$21.63	$21.65	$21.60
Purchase #4	$154.79	3.665%	$160.4631	$160.46	$160.45	$160.50
Purchase #5	$132.74	3.319%	$137.1456	$137.15	$137.15	$137.10
Purchase #6	$101.55	9.596%	$111.2947	$111.29	$111.30	$111.30
Purchase #7	$73.96	11.244%	$82.2761	$82.28	$82.30	$82.30
7 purchase totals =	$935.59		$987.4701	$987.47	$987.50	$987.40