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	$81.58	7.763%	$87.9131	$87.91	$87.90	$87.90
Purchase #2	$244.55	7.244%	$262.2652	$262.27	$262.25	$262.30
Purchase #3	$160.73	13.286%	$182.0846	$182.08	$182.10	$182.10
Purchase #4	$244.93	9.133%	$267.2995	$267.30	$267.30	$267.30
Purchase #5	$115.66	13.632%	$131.4268	$131.43	$131.45	$131.40
Purchase #6	$131.25	8.547%	$142.4679	$142.47	$142.45	$142.50
Purchase #7	$103.48	8.489%	$112.2644	$112.26	$112.25	$112.30
7 purchase totals =	$1,082.18		$1,185.7215	$1,185.72	$1,185.70	$1,185.80