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	$207.98	13.413%	$235.8764	$235.88	$235.90	$235.90
Purchase #2	$81.59	5.226%	$85.8539	$85.85	$85.85	$85.90
Purchase #3	$123.25	11.342%	$137.229	$137.23	$137.25	$137.20
Purchase #4	$203.90	7.732%	$219.6655	$219.67	$219.65	$219.70
Purchase #5	$180.99	10.642%	$200.251	$200.25	$200.25	$200.30
Purchase #6	$94.67	3.552%	$98.0327	$98.03	$98.05	$98.00
Purchase #7	$100.99	3.450%	$104.4742	$104.47	$104.45	$104.50
7 purchase totals =	$993.37		$1,081.3827	$1,081.38	$1,081.40	$1,081.50