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	$117.34	8.728%	$127.5814	$127.58	$127.60	$127.60
Purchase #2	$14.47	9.806%	$15.8889	$15.89	$15.90	$15.90
Purchase #3	$36.81	6.661%	$39.2619	$39.26	$39.25	$39.30
Purchase #4	$90.77	3.179%	$93.6556	$93.66	$93.65	$93.70
Purchase #5	$185.48	3.426%	$191.8345	$191.83	$191.85	$191.80
Purchase #6	$23.61	8.261%	$25.5604	$25.56	$25.55	$25.60
Purchase #7	$86.74	11.330%	$96.5676	$96.57	$96.55	$96.60
7 purchase totals =	$555.22		$590.3503	$590.35	$590.35	$590.50