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	$163.60	13.234%	$185.2508	$185.25	$185.25	$185.30
Purchase #2	$108.78	13.321%	$123.2706	$123.27	$123.25	$123.30
Purchase #3	$171.91	12.675%	$193.6996	$193.70	$193.70	$193.70
Purchase #4	$147.33	13.528%	$167.2608	$167.26	$167.25	$167.30
Purchase #5	$145.60	3.469%	$150.6509	$150.65	$150.65	$150.70
Purchase #6	$209.79	6.495%	$223.4159	$223.42	$223.40	$223.40
Purchase #7	$60.31	8.380%	$65.364	$65.36	$65.35	$65.40
7 purchase totals =	$1,007.32		$1,108.9126	$1,108.91	$1,108.85	$1,109.10