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	$238.45	6.523%	$254.0041	$254.00	$254.00	$254.00
Purchase #2	$170.59	11.427%	$190.0833	$190.08	$190.10	$190.10
Purchase #3	$163.28	9.618%	$178.9843	$178.98	$179.00	$179.00
Purchase #4	$154.27	9.260%	$168.5554	$168.56	$168.55	$168.60
Purchase #5	$81.53	13.683%	$92.6857	$92.69	$92.70	$92.70
Purchase #6	$231.83	10.625%	$256.4619	$256.46	$256.45	$256.50
Purchase #7	$90.46	12.122%	$101.4256	$101.43	$101.45	$101.40
7 purchase totals =	$1,130.41		$1,242.2003	$1,242.20	$1,242.25	$1,242.30