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	$27.41	6.659%	$29.2352	$29.24	$29.25	$29.20
Purchase #2	$244.73	7.382%	$262.796	$262.80	$262.80	$262.80
Purchase #3	$104.75	8.241%	$113.3824	$113.38	$113.40	$113.40
Purchase #4	$240.63	11.136%	$267.4266	$267.43	$267.45	$267.40
Purchase #5	$30.38	4.107%	$31.6277	$31.63	$31.65	$31.60
Purchase #6	$59.58	3.301%	$61.5467	$61.55	$61.55	$61.50
Purchase #7	$162.83	13.847%	$185.3771	$185.38	$185.40	$185.40
7 purchase totals =	$870.31		$951.3917	$951.41	$951.50	$951.30