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	$205.62	5.461%	$216.8489	$216.85	$216.85	$216.80
Purchase #2	$53.77	10.105%	$59.2035	$59.20	$59.20	$59.20
Purchase #3	$230.77	6.426%	$245.5993	$245.60	$245.60	$245.60
Purchase #4	$114.45	3.345%	$118.2784	$118.28	$118.30	$118.30
Purchase #5	$108.96	12.494%	$122.5735	$122.57	$122.55	$122.60
Purchase #6	$54.35	8.731%	$59.0953	$59.10	$59.10	$59.10
Purchase #7	$245.69	9.584%	$269.2369	$269.24	$269.25	$269.20
7 purchase totals =	$1,013.61		$1,090.8358	$1,090.84	$1,090.85	$1,090.80