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	$17.57	5.472%	$18.5314	$18.53	$18.55	$18.50
Purchase #2	$38.88	12.799%	$43.8563	$43.86	$43.85	$43.90
Purchase #3	$51.57	9.640%	$56.5413	$56.54	$56.55	$56.50
Purchase #4	$16.83	11.167%	$18.7094	$18.71	$18.70	$18.70
Purchase #5	$182.40	6.432%	$194.132	$194.13	$194.15	$194.10
Purchase #6	$37.27	8.557%	$40.4592	$40.46	$40.45	$40.50
Purchase #7	$171.96	11.713%	$192.1017	$192.10	$192.10	$192.10
7 purchase totals =	$516.48		$564.3313	$564.33	$564.35	$564.30