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	$152.68	13.396%	$173.133	$173.13	$173.15	$173.10
Purchase #2	$88.25	3.637%	$91.4597	$91.46	$91.45	$91.50
Purchase #3	$112.61	3.680%	$116.754	$116.75	$116.75	$116.80
Purchase #4	$181.69	3.367%	$187.8075	$187.81	$187.80	$187.80
Purchase #5	$29.54	5.870%	$31.274	$31.27	$31.25	$31.30
Purchase #6	$5.62	12.737%	$6.3358	$6.34	$6.35	$6.30
Purchase #7	$55.82	4.578%	$58.3754	$58.38	$58.40	$58.40
7 purchase totals =	$626.21		$665.1394	$665.14	$665.15	$665.20