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	$101.33	9.664%	$111.1225	$111.12	$111.10	$111.10
Purchase #2	$71.93	8.807%	$78.2649	$78.26	$78.25	$78.30
Purchase #3	$94.79	11.518%	$105.7079	$105.71	$105.70	$105.70
Purchase #4	$7.87	11.163%	$8.7485	$8.75	$8.75	$8.70
Purchase #5	$146.61	12.189%	$164.4803	$164.48	$164.50	$164.50
Purchase #6	$14.89	4.209%	$15.5167	$15.52	$15.50	$15.50
Purchase #7	$67.88	4.234%	$70.754	$70.75	$70.75	$70.80
7 purchase totals =	$505.30		$554.5948	$554.59	$554.55	$554.60