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	$151.85	3.162%	$156.6515	$156.65	$156.65	$156.70
Purchase #2	$17.31	5.601%	$18.2795	$18.28	$18.30	$18.30
Purchase #3	$189.37	4.825%	$198.5071	$198.51	$198.50	$198.50
Purchase #4	$183.41	9.374%	$200.6029	$200.60	$200.60	$200.60
Purchase #5	$214.63	12.539%	$241.5425	$241.54	$241.55	$241.50
Purchase #6	$150.89	9.393%	$165.0631	$165.06	$165.05	$165.10
Purchase #7	$109.32	12.569%	$123.0604	$123.06	$123.05	$123.10
7 purchase totals =	$1,016.78		$1,103.7070	$1,103.70	$1,103.70	$1,103.80