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	$71.32	3.282%	$73.6607	$73.66	$73.65	$73.70
Purchase #2	$183.42	7.340%	$196.883	$196.88	$196.90	$196.90
Purchase #3	$188.69	13.654%	$214.4537	$214.45	$214.45	$214.50
Purchase #4	$82.79	8.138%	$89.5275	$89.53	$89.55	$89.50
Purchase #5	$159.80	5.564%	$168.6913	$168.69	$168.70	$168.70
Purchase #6	$79.39	10.599%	$87.8045	$87.80	$87.80	$87.80
Purchase #7	$179.54	8.531%	$194.8566	$194.86	$194.85	$194.90
7 purchase totals =	$944.95		$1,025.8773	$1,025.87	$1,025.90	$1,026.00