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	$85.83	8.282%	$92.9384	$92.94	$92.95	$92.90
Purchase #2	$6.75	11.692%	$7.5392	$7.54	$7.55	$7.50
Purchase #3	$74.87	8.331%	$81.1074	$81.11	$81.10	$81.10
Purchase #4	$155.87	10.254%	$171.8529	$171.85	$171.85	$171.90
Purchase #5	$74.77	4.745%	$78.3178	$78.32	$78.30	$78.30
Purchase #6	$232.45	7.347%	$249.5281	$249.53	$249.55	$249.50
Purchase #7	$157.55	4.143%	$164.0773	$164.08	$164.10	$164.10
7 purchase totals =	$788.09		$845.3611	$845.37	$845.40	$845.30