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	$158.96	12.671%	$179.1018	$179.10	$179.10	$179.10
Purchase #2	$87.37	12.171%	$98.0038	$98.00	$98.00	$98.00
Purchase #3	$182.72	7.665%	$196.7255	$196.73	$196.75	$196.70
Purchase #4	$69.76	6.555%	$74.3328	$74.33	$74.35	$74.30
Purchase #5	$64.36	12.822%	$72.6122	$72.61	$72.60	$72.60
Purchase #6	$186.38	7.716%	$200.7611	$200.76	$200.75	$200.80
Purchase #7	$5.66	5.646%	$5.9796	$5.98	$6.00	$6.00
7 purchase totals =	$755.21		$827.5168	$827.51	$827.55	$827.50