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	$63.58	13.670%	$72.2714	$72.27	$72.25	$72.30
Purchase #2	$168.35	12.343%	$189.1294	$189.13	$189.15	$189.10
Purchase #3	$89.78	7.413%	$96.4354	$96.44	$96.45	$96.40
Purchase #4	$100.86	13.141%	$114.114	$114.11	$114.10	$114.10
Purchase #5	$80.90	4.583%	$84.6076	$84.61	$84.60	$84.60
Purchase #6	$249.68	10.688%	$276.3658	$276.37	$276.35	$276.40
Purchase #7	$150.62	12.394%	$169.2878	$169.29	$169.30	$169.30
7 purchase totals =	$903.77		$1,002.2114	$1,002.22	$1,002.20	$1,002.20