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	$177.27	10.670%	$196.1847	$196.18	$196.20	$196.20
Purchase #2	$99.45	4.769%	$104.1928	$104.19	$104.20	$104.20
Purchase #3	$148.45	11.464%	$165.4683	$165.47	$165.45	$165.50
Purchase #4	$161.72	5.864%	$171.2033	$171.20	$171.20	$171.20
Purchase #5	$151.55	11.360%	$168.7661	$168.77	$168.75	$168.80
Purchase #6	$166.92	6.681%	$178.0719	$178.07	$178.05	$178.10
Purchase #7	$110.40	9.222%	$120.5811	$120.58	$120.60	$120.60
7 purchase totals =	$1,015.76		$1,104.4682	$1,104.46	$1,104.45	$1,104.60