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	$124.25	4.193%	$129.4598	$129.46	$129.45	$129.50
Purchase #2	$243.70	4.835%	$255.4829	$255.48	$255.50	$255.50
Purchase #3	$130.62	7.411%	$140.3002	$140.30	$140.30	$140.30
Purchase #4	$44.30	13.830%	$50.4267	$50.43	$50.45	$50.40
Purchase #5	$200.32	4.130%	$208.5932	$208.59	$208.60	$208.60
Purchase #6	$26.40	4.208%	$27.5109	$27.51	$27.50	$27.50
Purchase #7	$49.49	11.716%	$55.2882	$55.29	$55.30	$55.30
7 purchase totals =	$819.08		$867.0619	$867.06	$867.10	$867.10