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	$176.38	6.593%	$188.0087	$188.01	$188.00	$188.00
Purchase #2	$48.96	10.659%	$54.1786	$54.18	$54.20	$54.20
Purchase #3	$147.96	8.373%	$160.3487	$160.35	$160.35	$160.30
Purchase #4	$119.96	12.445%	$134.889	$134.89	$134.90	$134.90
Purchase #5	$11.72	5.280%	$12.3388	$12.34	$12.35	$12.30
Purchase #6	$100.60	4.506%	$105.133	$105.13	$105.15	$105.10
Purchase #7	$79.97	8.225%	$86.5475	$86.55	$86.55	$86.50
7 purchase totals =	$685.55		$741.4443	$741.45	$741.50	$741.30