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	$180.63	8.810%	$196.5435	$196.54	$196.55	$196.50
Purchase #2	$135.55	5.333%	$142.7789	$142.78	$142.80	$142.80
Purchase #3	$117.96	4.537%	$123.3118	$123.31	$123.30	$123.30
Purchase #4	$79.51	7.570%	$85.5289	$85.53	$85.55	$85.50
Purchase #5	$247.87	8.706%	$269.4496	$269.45	$269.45	$269.40
Purchase #6	$59.51	6.314%	$63.2675	$63.27	$63.25	$63.30
Purchase #7	$148.97	13.160%	$168.5745	$168.57	$168.55	$168.60
7 purchase totals =	$970.00		$1,049.4547	$1,049.45	$1,049.45	$1,049.40