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	$114.79	3.479%	$118.7835	$118.78	$118.80	$118.80
Purchase #2	$187.84	6.511%	$200.0703	$200.07	$200.05	$200.10
Purchase #3	$123.73	3.171%	$127.6535	$127.65	$127.65	$127.70
Purchase #4	$25.86	7.112%	$27.6992	$27.70	$27.70	$27.70
Purchase #5	$37.48	8.651%	$40.7224	$40.72	$40.70	$40.70
Purchase #6	$207.88	9.606%	$227.849	$227.85	$227.85	$227.80
Purchase #7	$101.33	5.198%	$106.5971	$106.60	$106.60	$106.60
7 purchase totals =	$798.91		$849.3750	$849.37	$849.35	$849.40