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	$218.60	7.172%	$234.278	$234.28	$234.30	$234.30
Purchase #2	$45.84	4.570%	$47.9349	$47.93	$47.95	$47.90
Purchase #3	$124.61	5.438%	$131.3863	$131.39	$131.40	$131.40
Purchase #4	$47.38	10.422%	$52.3179	$52.32	$52.30	$52.30
Purchase #5	$233.73	5.167%	$245.8068	$245.81	$245.80	$245.80
Purchase #6	$227.45	6.256%	$241.6793	$241.68	$241.70	$241.70
Purchase #7	$85.69	12.737%	$96.6043	$96.60	$96.60	$96.60
7 purchase totals =	$983.30		$1,050.0075	$1,050.01	$1,050.05	$1,050.00