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	$245.36	10.326%	$270.6959	$270.70	$270.70	$270.70
Purchase #2	$70.30	11.206%	$78.1778	$78.18	$78.20	$78.20
Purchase #3	$249.50	5.771%	$263.8986	$263.90	$263.90	$263.90
Purchase #4	$48.66	5.856%	$51.5095	$51.51	$51.50	$51.50
Purchase #5	$131.93	8.294%	$142.8723	$142.87	$142.85	$142.90
Purchase #6	$212.70	9.791%	$233.5255	$233.53	$233.55	$233.50
Purchase #7	$94.97	10.135%	$104.5952	$104.60	$104.60	$104.60
7 purchase totals =	$1,053.42		$1,145.2748	$1,145.29	$1,145.30	$1,145.30