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	$99.64	7.781%	$107.393	$107.39	$107.40	$107.40
Purchase #2	$17.40	6.139%	$18.4682	$18.47	$18.45	$18.50
Purchase #3	$68.95	5.352%	$72.6402	$72.64	$72.65	$72.60
Purchase #4	$32.96	5.849%	$34.8878	$34.89	$34.90	$34.90
Purchase #5	$74.31	5.707%	$78.5509	$78.55	$78.55	$78.60
Purchase #6	$234.53	6.288%	$249.2772	$249.28	$249.30	$249.30
Purchase #7	$221.26	13.499%	$251.1279	$251.13	$251.15	$251.10
7 purchase totals =	$749.05		$812.3452	$812.35	$812.40	$812.40