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	$107.71	4.346%	$112.3911	$112.39	$112.40	$112.40
Purchase #2	$53.33	8.571%	$57.9009	$57.90	$57.90	$57.90
Purchase #3	$168.33	11.604%	$187.863	$187.86	$187.85	$187.90
Purchase #4	$117.43	8.672%	$127.6135	$127.61	$127.60	$127.60
Purchase #5	$25.81	7.825%	$27.8296	$27.83	$27.85	$27.80
Purchase #6	$185.94	7.165%	$199.2626	$199.26	$199.25	$199.30
Purchase #7	$76.44	11.485%	$85.2191	$85.22	$85.20	$85.20
7 purchase totals =	$734.99		$798.0798	$798.07	$798.05	$798.10