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	$189.31	3.639%	$196.199	$196.20	$196.20	$196.20
Purchase #2	$10.39	9.205%	$11.3464	$11.35	$11.35	$11.30
Purchase #3	$24.71	11.695%	$27.5998	$27.60	$27.60	$27.60
Purchase #4	$51.73	11.863%	$57.8667	$57.87	$57.85	$57.90
Purchase #5	$133.79	11.866%	$149.6655	$149.67	$149.65	$149.70
Purchase #6	$72.34	13.797%	$82.3207	$82.32	$82.30	$82.30
Purchase #7	$222.71	11.830%	$249.0566	$249.06	$249.05	$249.10
7 purchase totals =	$704.98		$774.0547	$774.07	$774.00	$774.10