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	$50.36	5.346%	$53.0522	$53.05	$53.05	$53.10
Purchase #2	$58.73	8.249%	$63.5746	$63.57	$63.55	$63.60
Purchase #3	$126.79	8.855%	$138.0173	$138.02	$138.00	$138.00
Purchase #4	$190.81	3.155%	$196.8301	$196.83	$196.85	$196.80
Purchase #5	$236.37	11.269%	$263.0065	$263.01	$263.00	$263.00
Purchase #6	$234.55	6.497%	$249.7887	$249.79	$249.80	$249.80
Purchase #7	$91.28	6.272%	$97.0051	$97.01	$97.00	$97.00
7 purchase totals =	$988.89		$1,061.2745	$1,061.28	$1,061.25	$1,061.30