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	$176.77	5.181%	$185.9285	$185.93	$185.95	$185.90
Purchase #2	$85.84	12.303%	$96.4009	$96.40	$96.40	$96.40
Purchase #3	$7.65	5.257%	$8.0522	$8.05	$8.05	$8.10
Purchase #4	$189.91	3.451%	$196.4638	$196.46	$196.45	$196.50
Purchase #5	$244.49	6.166%	$259.5653	$259.57	$259.55	$259.60
Purchase #6	$95.69	7.167%	$102.5481	$102.55	$102.55	$102.50
Purchase #7	$58.37	9.463%	$63.8936	$63.89	$63.90	$63.90
7 purchase totals =	$858.72		$912.8524	$912.85	$912.85	$912.90