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	$181.90	8.232%	$196.874	$196.87	$196.85	$196.90
Purchase #2	$240.50	6.831%	$256.9286	$256.93	$256.95	$256.90
Purchase #3	$60.70	11.185%	$67.4893	$67.49	$67.50	$67.50
Purchase #4	$64.28	4.466%	$67.1507	$67.15	$67.15	$67.20
Purchase #5	$212.31	5.455%	$223.8915	$223.89	$223.90	$223.90
Purchase #6	$38.59	12.260%	$43.3211	$43.32	$43.30	$43.30
Purchase #7	$213.54	9.375%	$233.5594	$233.56	$233.55	$233.60
7 purchase totals =	$1,011.82		$1,089.2146	$1,089.21	$1,089.20	$1,089.30