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	$167.57	5.581%	$176.9221	$176.92	$176.90	$176.90
Purchase #2	$103.26	6.242%	$109.7055	$109.71	$109.70	$109.70
Purchase #3	$29.78	7.190%	$31.9212	$31.92	$31.90	$31.90
Purchase #4	$240.91	8.858%	$262.2498	$262.25	$262.25	$262.20
Purchase #5	$58.30	5.526%	$61.5217	$61.52	$61.50	$61.50
Purchase #6	$26.69	7.295%	$28.637	$28.64	$28.65	$28.60
Purchase #7	$97.89	7.618%	$105.3473	$105.35	$105.35	$105.30
7 purchase totals =	$724.40		$776.3046	$776.31	$776.25	$776.10