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	$147.68	4.558%	$154.4113	$154.41	$154.40	$154.40
Purchase #2	$25.43	6.573%	$27.1015	$27.10	$27.10	$27.10
Purchase #3	$97.30	12.414%	$109.3788	$109.38	$109.40	$109.40
Purchase #4	$139.48	9.307%	$152.4614	$152.46	$152.45	$152.50
Purchase #5	$215.82	4.666%	$225.8902	$225.89	$225.90	$225.90
Purchase #6	$11.82	11.164%	$13.1396	$13.14	$13.15	$13.10
Purchase #7	$209.36	3.742%	$217.1943	$217.19	$217.20	$217.20
7 purchase totals =	$846.89		$899.5771	$899.57	$899.60	$899.60