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	$171.27	3.843%	$177.8519	$177.85	$177.85	$177.90
Purchase #2	$165.27	4.422%	$172.5782	$172.58	$172.60	$172.60
Purchase #3	$85.89	5.525%	$90.6354	$90.64	$90.65	$90.60
Purchase #4	$200.48	7.272%	$215.0589	$215.06	$215.05	$215.10
Purchase #5	$127.45	9.290%	$139.2901	$139.29	$139.30	$139.30
Purchase #6	$152.64	8.318%	$165.3366	$165.34	$165.35	$165.30
Purchase #7	$188.98	7.139%	$202.4713	$202.47	$202.45	$202.50
7 purchase totals =	$1,091.98		$1,163.2224	$1,163.23	$1,163.25	$1,163.30