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	$162.37	5.516%	$171.3263	$171.33	$171.35	$171.30
Purchase #2	$72.42	7.797%	$78.0666	$78.07	$78.05	$78.10
Purchase #3	$205.81	12.655%	$231.8553	$231.86	$231.85	$231.90
Purchase #4	$239.58	11.835%	$267.9343	$267.93	$267.95	$267.90
Purchase #5	$116.47	6.509%	$124.051	$124.05	$124.05	$124.10
Purchase #6	$81.63	9.418%	$89.3179	$89.32	$89.30	$89.30
Purchase #7	$95.81	12.294%	$107.5889	$107.59	$107.60	$107.60
7 purchase totals =	$974.09		$1,070.1403	$1,070.15	$1,070.15	$1,070.20