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	$229.78	12.374%	$258.213	$258.21	$258.20	$258.20
Purchase #2	$164.55	4.824%	$172.4879	$172.49	$172.50	$172.50
Purchase #3	$103.95	7.372%	$111.6132	$111.61	$111.60	$111.60
Purchase #4	$242.96	5.110%	$255.3753	$255.38	$255.40	$255.40
Purchase #5	$35.64	4.832%	$37.3621	$37.36	$37.35	$37.40
Purchase #6	$30.44	11.381%	$33.9044	$33.90	$33.90	$33.90
Purchase #7	$159.50	6.225%	$169.4289	$169.43	$169.45	$169.40
7 purchase totals =	$966.82		$1,038.3848	$1,038.38	$1,038.40	$1,038.40