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	$186.85	6.367%	$198.7467	$198.75	$198.75	$198.70
Purchase #2	$103.59	5.547%	$109.3361	$109.34	$109.35	$109.30
Purchase #3	$31.59	10.333%	$34.8542	$34.85	$34.85	$34.90
Purchase #4	$41.57	4.772%	$43.5537	$43.55	$43.55	$43.60
Purchase #5	$179.81	11.669%	$200.792	$200.79	$200.80	$200.80
Purchase #6	$22.33	10.499%	$24.6744	$24.67	$24.65	$24.70
Purchase #7	$52.63	9.632%	$57.6993	$57.70	$57.70	$57.70
7 purchase totals =	$618.37		$669.6564	$669.65	$669.65	$669.70