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	$249.45	5.220%	$262.4713	$262.47	$262.45	$262.50
Purchase #2	$144.75	4.250%	$150.9019	$150.90	$150.90	$150.90
Purchase #3	$60.62	9.132%	$66.1558	$66.16	$66.15	$66.20
Purchase #4	$176.54	8.475%	$191.5018	$191.50	$191.50	$191.50
Purchase #5	$174.82	6.552%	$186.2742	$186.27	$186.25	$186.30
Purchase #6	$7.66	4.748%	$8.0237	$8.02	$8.00	$8.00
Purchase #7	$131.59	10.132%	$144.9227	$144.92	$144.90	$144.90
7 purchase totals =	$945.43		$1,010.2514	$1,010.24	$1,010.15	$1,010.30